1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
// This is a part of Chrono.
// See README.md and LICENSE.txt for details.

//! # Chrono: Date and Time for Rust
//!
//! It aims to be a feature-complete superset of
//! the [time](https://github.com/rust-lang-deprecated/time) library.
//! In particular,
//!
//! * Chrono strictly adheres to ISO 8601.
//! * Chrono is timezone-aware by default, with separate timezone-naive types.
//! * Chrono is space-optimal and (while not being the primary goal) reasonably efficient.
//!
//! There were several previous attempts to bring a good date and time library to Rust,
//! which Chrono builds upon and should acknowledge:
//!
//! * [Initial research on
//!    the wiki](https://github.com/rust-lang/rust-wiki-backup/blob/master/Lib-datetime.md)
//! * Dietrich Epp's [datetime-rs](https://github.com/depp/datetime-rs)
//! * Luis de Bethencourt's [rust-datetime](https://github.com/luisbg/rust-datetime)
//!
//! Any significant changes to Chrono are documented in
//! the [`CHANGELOG.md`](https://github.com/chronotope/chrono/blob/main/CHANGELOG.md) file.
//!
//! ## Usage
//!
//! Put this in your `Cargo.toml`:
//!
//! ```toml
//! [dependencies]
//! chrono = "0.4"
//! ```
//!
//! ### Features
//!
//! Chrono supports various runtime environments and operating systems, and has
//! several features that may be enabled or disabled.
//!
//! Default features:
//!
//! - `alloc`: Enable features that depend on allocation (primarily string formatting)
//! - `std`: Enables functionality that depends on the standard library. This
//!   is a superset of `alloc` and adds interoperation with standard library types
//!   and traits.
//! - `clock`: enables reading the system time (`now`), independent of whether
//!   `std::time::SystemTime` is present, depends on having a libc.
//!
//! Optional features:
//!
//! - `wasmbind`: Enable integration with [wasm-bindgen][] and its `js-sys` project
//! - [`serde`][]: Enable serialization/deserialization via serde.
//! - `unstable-locales`: Enable localization. This adds various methods with a
//!   `_localized` suffix. The implementation and API may change or even be
//!   removed in a patch release. Feedback welcome.
//!
//! [`serde`]: https://github.com/serde-rs/serde
//! [wasm-bindgen]: https://github.com/rustwasm/wasm-bindgen
//!
//! See the [cargo docs][] for examples of specifying features.
//!
//! [cargo docs]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#choosing-features
//!
//! ## Overview
//!
//! ### Duration
//!
//! Chrono currently uses its own [`Duration`] type to represent the magnitude
//! of a time span. Since this has the same name as the newer, standard type for
//! duration, the reference will refer this type as `OldDuration`.
//!
//! Note that this is an "accurate" duration represented as seconds and
//! nanoseconds and does not represent "nominal" components such as days or
//! months.
//!
//! When the `oldtime` feature is enabled, [`Duration`] is an alias for the
//! [`time::Duration`](https://docs.rs/time/0.1.40/time/struct.Duration.html)
//! type from v0.1 of the time crate. time v0.1 is deprecated, so new code
//! should disable the `oldtime` feature and use the `chrono::Duration` type
//! instead. The `oldtime` feature is enabled by default for backwards
//! compatibility, but future versions of Chrono are likely to remove the
//! feature entirely.
//!
//! Chrono does not yet natively support
//! the standard [`Duration`](https://doc.rust-lang.org/std/time/struct.Duration.html) type,
//! but it will be supported in the future.
//! Meanwhile you can convert between two types with
//! [`Duration::from_std`](https://docs.rs/time/0.1.40/time/struct.Duration.html#method.from_std)
//! and
//! [`Duration::to_std`](https://docs.rs/time/0.1.40/time/struct.Duration.html#method.to_std)
//! methods.
//!
//! ### Date and Time
//!
//! Chrono provides a
//! [**`DateTime`**](./struct.DateTime.html)
//! type to represent a date and a time in a timezone.
//!
//! For more abstract moment-in-time tracking such as internal timekeeping
//! that is unconcerned with timezones, consider
//! [`time::SystemTime`](https://doc.rust-lang.org/std/time/struct.SystemTime.html),
//! which tracks your system clock, or
//! [`time::Instant`](https://doc.rust-lang.org/std/time/struct.Instant.html), which
//! is an opaque but monotonically-increasing representation of a moment in time.
//!
//! `DateTime` is timezone-aware and must be constructed from
//! the [**`TimeZone`**](./offset/trait.TimeZone.html) object,
//! which defines how the local date is converted to and back from the UTC date.
//! There are three well-known `TimeZone` implementations:
//!
//! * [**`Utc`**](./offset/struct.Utc.html) specifies the UTC time zone. It is most efficient.
//!
//! * [**`Local`**](./offset/struct.Local.html) specifies the system local time zone.
//!
//! * [**`FixedOffset`**](./offset/struct.FixedOffset.html) specifies
//!   an arbitrary, fixed time zone such as UTC+09:00 or UTC-10:30.
//!   This often results from the parsed textual date and time.
//!   Since it stores the most information and does not depend on the system environment,
//!   you would want to normalize other `TimeZone`s into this type.
//!
//! `DateTime`s with different `TimeZone` types are distinct and do not mix,
//! but can be converted to each other using
//! the [`DateTime::with_timezone`](./struct.DateTime.html#method.with_timezone) method.
//!
//! You can get the current date and time in the UTC time zone
//! ([`Utc::now()`](./offset/struct.Utc.html#method.now))
//! or in the local time zone
//! ([`Local::now()`](./offset/struct.Local.html#method.now)).
//!
//! ```rust
//! use chrono::prelude::*;
//!
//! let utc: DateTime<Utc> = Utc::now();       // e.g. `2014-11-28T12:45:59.324310806Z`
//! let local: DateTime<Local> = Local::now(); // e.g. `2014-11-28T21:45:59.324310806+09:00`
//! # let _ = utc; let _ = local;
//! ```
//!
//! Alternatively, you can create your own date and time.
//! This is a bit verbose due to Rust's lack of function and method overloading,
//! but in turn we get a rich combination of initialization methods.
//!
//! ```rust
//! use chrono::prelude::*;
//! use chrono::offset::LocalResult;
//!
//! let dt = Utc.ymd(2014, 7, 8).and_hms(9, 10, 11); // `2014-07-08T09:10:11Z`
//! // July 8 is 188th day of the year 2014 (`o` for "ordinal")
//! assert_eq!(dt, Utc.yo(2014, 189).and_hms(9, 10, 11));
//! // July 8 is Tuesday in ISO week 28 of the year 2014.
//! assert_eq!(dt, Utc.isoywd(2014, 28, Weekday::Tue).and_hms(9, 10, 11));
//!
//! let dt = Utc.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12); // `2014-07-08T09:10:11.012Z`
//! assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_micro(9, 10, 11, 12_000));
//! assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_nano(9, 10, 11, 12_000_000));
//!
//! // dynamic verification
//! assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(21, 15, 33),
//!            LocalResult::Single(Utc.ymd(2014, 7, 8).and_hms(21, 15, 33)));
//! assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(80, 15, 33), LocalResult::None);
//! assert_eq!(Utc.ymd_opt(2014, 7, 38).and_hms_opt(21, 15, 33), LocalResult::None);
//!
//! // other time zone objects can be used to construct a local datetime.
//! // obviously, `local_dt` is normally different from `dt`, but `fixed_dt` should be identical.
//! let local_dt = Local.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12);
//! let fixed_dt = FixedOffset::east(9 * 3600).ymd(2014, 7, 8).and_hms_milli(18, 10, 11, 12);
//! assert_eq!(dt, fixed_dt);
//! # let _ = local_dt;
//! ```
//!
//! Various properties are available to the date and time, and can be altered individually.
//! Most of them are defined in the traits [`Datelike`](./trait.Datelike.html) and
//! [`Timelike`](./trait.Timelike.html) which you should `use` before.
//! Addition and subtraction is also supported.
//! The following illustrates most supported operations to the date and time:
//!
//! ```rust
//! # extern crate chrono;
//!
//! # fn main() {
//! use chrono::prelude::*;
//! use chrono::Duration;
//!
//! // assume this returned `2014-11-28T21:45:59.324310806+09:00`:
//! let dt = FixedOffset::east(9*3600).ymd(2014, 11, 28).and_hms_nano(21, 45, 59, 324310806);
//!
//! // property accessors
//! assert_eq!((dt.year(), dt.month(), dt.day()), (2014, 11, 28));
//! assert_eq!((dt.month0(), dt.day0()), (10, 27)); // for unfortunate souls
//! assert_eq!((dt.hour(), dt.minute(), dt.second()), (21, 45, 59));
//! assert_eq!(dt.weekday(), Weekday::Fri);
//! assert_eq!(dt.weekday().number_from_monday(), 5); // Mon=1, ..., Sun=7
//! assert_eq!(dt.ordinal(), 332); // the day of year
//! assert_eq!(dt.num_days_from_ce(), 735565); // the number of days from and including Jan 1, 1
//!
//! // time zone accessor and manipulation
//! assert_eq!(dt.offset().fix().local_minus_utc(), 9 * 3600);
//! assert_eq!(dt.timezone(), FixedOffset::east(9 * 3600));
//! assert_eq!(dt.with_timezone(&Utc), Utc.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
//!
//! // a sample of property manipulations (validates dynamically)
//! assert_eq!(dt.with_day(29).unwrap().weekday(), Weekday::Sat); // 2014-11-29 is Saturday
//! assert_eq!(dt.with_day(32), None);
//! assert_eq!(dt.with_year(-300).unwrap().num_days_from_ce(), -109606); // November 29, 301 BCE
//!
//! // arithmetic operations
//! let dt1 = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
//! let dt2 = Utc.ymd(2014, 11, 14).and_hms(10, 9, 8);
//! assert_eq!(dt1.signed_duration_since(dt2), Duration::seconds(-2 * 3600 + 2));
//! assert_eq!(dt2.signed_duration_since(dt1), Duration::seconds(2 * 3600 - 2));
//! assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) + Duration::seconds(1_000_000_000),
//!            Utc.ymd(2001, 9, 9).and_hms(1, 46, 40));
//! assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) - Duration::seconds(1_000_000_000),
//!            Utc.ymd(1938, 4, 24).and_hms(22, 13, 20));
//! # }
//! ```
//!
//! ### Formatting and Parsing
//!
//! Formatting is done via the [`format`](./struct.DateTime.html#method.format) method,
//! which format is equivalent to the familiar `strftime` format.
//!
//! See [`format::strftime`](./format/strftime/index.html#specifiers)
//! documentation for full syntax and list of specifiers.
//!
//! The default `to_string` method and `{:?}` specifier also give a reasonable representation.
//! Chrono also provides [`to_rfc2822`](./struct.DateTime.html#method.to_rfc2822) and
//! [`to_rfc3339`](./struct.DateTime.html#method.to_rfc3339) methods
//! for well-known formats.
//!
//! Chrono now also provides date formatting in almost any language without the
//! help of an additional C library. This functionality is under the feature
//! `unstable-locales`:
//!
//! ```text
//! chrono { version = "0.4", features = ["unstable-locales"]
//! ```
//!
//! The `unstable-locales` feature requires and implies at least the `alloc` feature.
//!
//! ```rust
//! use chrono::prelude::*;
//!
//! let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
//! assert_eq!(dt.format("%Y-%m-%d %H:%M:%S").to_string(), "2014-11-28 12:00:09");
//! assert_eq!(dt.format("%a %b %e %T %Y").to_string(), "Fri Nov 28 12:00:09 2014");
//! assert_eq!(dt.format_localized("%A %e %B %Y, %T", Locale::fr_BE).to_string(), "vendredi 28 novembre 2014, 12:00:09");
//! assert_eq!(dt.format("%a %b %e %T %Y").to_string(), dt.format("%c").to_string());
//!
//! assert_eq!(dt.to_string(), "2014-11-28 12:00:09 UTC");
//! assert_eq!(dt.to_rfc2822(), "Fri, 28 Nov 2014 12:00:09 +0000");
//! assert_eq!(dt.to_rfc3339(), "2014-11-28T12:00:09+00:00");
//! assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
//!
//! // Note that milli/nanoseconds are only printed if they are non-zero
//! let dt_nano = Utc.ymd(2014, 11, 28).and_hms_nano(12, 0, 9, 1);
//! assert_eq!(format!("{:?}", dt_nano), "2014-11-28T12:00:09.000000001Z");
//! ```
//!
//! Parsing can be done with three methods:
//!
//! 1. The standard [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) trait
//!    (and [`parse`](https://doc.rust-lang.org/std/primitive.str.html#method.parse) method
//!    on a string) can be used for parsing `DateTime<FixedOffset>`, `DateTime<Utc>` and
//!    `DateTime<Local>` values. This parses what the `{:?}`
//!    ([`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html))
//!    format specifier prints, and requires the offset to be present.
//!
//! 2. [`DateTime::parse_from_str`](./struct.DateTime.html#method.parse_from_str) parses
//!    a date and time with offsets and returns `DateTime<FixedOffset>`.
//!    This should be used when the offset is a part of input and the caller cannot guess that.
//!    It *cannot* be used when the offset can be missing.
//!    [`DateTime::parse_from_rfc2822`](./struct.DateTime.html#method.parse_from_rfc2822)
//!    and
//!    [`DateTime::parse_from_rfc3339`](./struct.DateTime.html#method.parse_from_rfc3339)
//!    are similar but for well-known formats.
//!
//! 3. [`Offset::datetime_from_str`](./offset/trait.TimeZone.html#method.datetime_from_str) is
//!    similar but returns `DateTime` of given offset.
//!    When the explicit offset is missing from the input, it simply uses given offset.
//!    It issues an error when the input contains an explicit offset different
//!    from the current offset.
//!
//! More detailed control over the parsing process is available via
//! [`format`](./format/index.html) module.
//!
//! ```rust
//! use chrono::prelude::*;
//!
//! let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
//! let fixed_dt = dt.with_timezone(&FixedOffset::east(9*3600));
//!
//! // method 1
//! assert_eq!("2014-11-28T12:00:09Z".parse::<DateTime<Utc>>(), Ok(dt.clone()));
//! assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<Utc>>(), Ok(dt.clone()));
//! assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<FixedOffset>>(), Ok(fixed_dt.clone()));
//!
//! // method 2
//! assert_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00", "%Y-%m-%d %H:%M:%S %z"),
//!            Ok(fixed_dt.clone()));
//! assert_eq!(DateTime::parse_from_rfc2822("Fri, 28 Nov 2014 21:00:09 +0900"),
//!            Ok(fixed_dt.clone()));
//! assert_eq!(DateTime::parse_from_rfc3339("2014-11-28T21:00:09+09:00"), Ok(fixed_dt.clone()));
//!
//! // method 3
//! assert_eq!(Utc.datetime_from_str("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone()));
//! assert_eq!(Utc.datetime_from_str("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));
//!
//! // oops, the year is missing!
//! assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T %Y").is_err());
//! // oops, the format string does not include the year at all!
//! assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T").is_err());
//! // oops, the weekday is incorrect!
//! assert!(Utc.datetime_from_str("Sat Nov 28 12:00:09 2014", "%a %b %e %T %Y").is_err());
//! ```
//!
//! Again : See [`format::strftime`](./format/strftime/index.html#specifiers)
//! documentation for full syntax and list of specifiers.
//!
//! ### Conversion from and to EPOCH timestamps
//!
//! Use [`Utc.timestamp(seconds, nanoseconds)`](./offset/trait.TimeZone.html#method.timestamp)
//! to construct a [`DateTime<Utc>`](./struct.DateTime.html) from a UNIX timestamp
//! (seconds, nanoseconds that passed since January 1st 1970).
//!
//! Use [`DateTime.timestamp`](./struct.DateTime.html#method.timestamp) to get the timestamp (in seconds)
//! from a [`DateTime`](./struct.DateTime.html). Additionally, you can use
//! [`DateTime.timestamp_subsec_nanos`](./struct.DateTime.html#method.timestamp_subsec_nanos)
//! to get the number of additional number of nanoseconds.
//!
//! ```rust
//! // We need the trait in scope to use Utc::timestamp().
//! use chrono::{DateTime, TimeZone, Utc};
//!
//! // Construct a datetime from epoch:
//! let dt = Utc.timestamp(1_500_000_000, 0);
//! assert_eq!(dt.to_rfc2822(), "Fri, 14 Jul 2017 02:40:00 +0000");
//!
//! // Get epoch value from a datetime:
//! let dt = DateTime::parse_from_rfc2822("Fri, 14 Jul 2017 02:40:00 +0000").unwrap();
//! assert_eq!(dt.timestamp(), 1_500_000_000);
//! ```
//!
//! ### Individual date
//!
//! Chrono also provides an individual date type ([**`Date`**](./struct.Date.html)).
//! It also has time zones attached, and have to be constructed via time zones.
//! Most operations available to `DateTime` are also available to `Date` whenever appropriate.
//!
//! ```rust
//! use chrono::prelude::*;
//! use chrono::offset::LocalResult;
//!
//! # // these *may* fail, but only very rarely. just rerun the test if you were that unfortunate ;)
//! assert_eq!(Utc::today(), Utc::now().date());
//! assert_eq!(Local::today(), Local::now().date());
//!
//! assert_eq!(Utc.ymd(2014, 11, 28).weekday(), Weekday::Fri);
//! assert_eq!(Utc.ymd_opt(2014, 11, 31), LocalResult::None);
//! assert_eq!(Utc.ymd(2014, 11, 28).and_hms_milli(7, 8, 9, 10).format("%H%M%S").to_string(),
//!            "070809");
//! ```
//!
//! There is no timezone-aware `Time` due to the lack of usefulness and also the complexity.
//!
//! `DateTime` has [`date`](./struct.DateTime.html#method.date) method
//! which returns a `Date` which represents its date component.
//! There is also a [`time`](./struct.DateTime.html#method.time) method,
//! which simply returns a naive local time described below.
//!
//! ### Naive date and time
//!
//! Chrono provides naive counterparts to `Date`, (non-existent) `Time` and `DateTime`
//! as [**`NaiveDate`**](./naive/struct.NaiveDate.html),
//! [**`NaiveTime`**](./naive/struct.NaiveTime.html) and
//! [**`NaiveDateTime`**](./naive/struct.NaiveDateTime.html) respectively.
//!
//! They have almost equivalent interfaces as their timezone-aware twins,
//! but are not associated to time zones obviously and can be quite low-level.
//! They are mostly useful for building blocks for higher-level types.
//!
//! Timezone-aware `DateTime` and `Date` types have two methods returning naive versions:
//! [`naive_local`](./struct.DateTime.html#method.naive_local) returns
//! a view to the naive local time,
//! and [`naive_utc`](./struct.DateTime.html#method.naive_utc) returns
//! a view to the naive UTC time.
//!
//! ## Limitations
//!
//! Only proleptic Gregorian calendar (i.e. extended to support older dates) is supported.
//! Be very careful if you really have to deal with pre-20C dates, they can be in Julian or others.
//!
//! Date types are limited in about +/- 262,000 years from the common epoch.
//! Time types are limited in the nanosecond accuracy.
//!
//! [Leap seconds are supported in the representation but
//! Chrono doesn't try to make use of them](./naive/struct.NaiveTime.html#leap-second-handling).
//! (The main reason is that leap seconds are not really predictable.)
//! Almost *every* operation over the possible leap seconds will ignore them.
//! Consider using `NaiveDateTime` with the implicit TAI (International Atomic Time) scale
//! if you want.
//!
//! Chrono inherently does not support an inaccurate or partial date and time representation.
//! Any operation that can be ambiguous will return `None` in such cases.
//! For example, "a month later" of 2014-01-30 is not well-defined
//! and consequently `Utc.ymd(2014, 1, 30).with_month(2)` returns `None`.
//!
//! Non ISO week handling is not yet supported.
//! For now you can use the [chrono_ext](https://crates.io/crates/chrono_ext)
//! crate ([sources](https://github.com/bcourtine/chrono-ext/)).
//!
//! Advanced time zone handling is not yet supported.
//! For now you can try the [Chrono-tz](https://github.com/chronotope/chrono-tz/) crate instead.

#![doc(html_root_url = "https://docs.rs/chrono/latest/")]
#![cfg_attr(feature = "bench", feature(test))] // lib stability features as per RFC #507
#![deny(missing_docs)]
#![deny(missing_debug_implementations)]
#![deny(dead_code)]
// lints are added all the time, we test on 1.13
#![allow(unknown_lints)]
#![cfg_attr(not(any(feature = "std", test)), no_std)]
#![cfg_attr(feature = "cargo-clippy", allow(
    renamed_and_removed_lints,
    // The explicit 'static lifetimes are still needed for rustc 1.13-16
    // backward compatibility, and this appeases clippy. If minimum rustc
    // becomes 1.17, should be able to remove this, those 'static lifetimes,
    // and use `static` in a lot of places `const` is used now.
    redundant_static_lifetimes,
    // Similarly, redundant_field_names lints on not using the
    // field-init-shorthand, which was stabilized in rust 1.17.
    redundant_field_names,
    // Changing trivially_copy_pass_by_ref would require an incompatible version
    // bump.
    trivially_copy_pass_by_ref,
    try_err,
    // Currently deprecated, we use the separate implementation to add docs
    // warning that putting a time in a hash table is probably a bad idea
    derive_hash_xor_eq,
))]

#[cfg(feature = "alloc")]
extern crate alloc;
#[cfg(all(feature = "std", not(feature = "alloc")))]
extern crate std as alloc;
#[cfg(any(feature = "std", test))]
extern crate std as core;

#[cfg(feature = "oldtime")]
extern crate time as oldtime;
#[cfg(not(feature = "oldtime"))]
mod oldtime;

#[cfg(feature = "clock")]
extern crate libc;
#[cfg(all(feature = "clock", windows))]
extern crate winapi;
#[cfg(all(
    feature = "clock",
    not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))
))]
mod sys;

extern crate num_integer;
extern crate num_traits;
#[cfg(feature = "rustc-serialize")]
extern crate rustc_serialize;
#[cfg(feature = "serde")]
extern crate serde as serdelib;
#[cfg(feature = "__doctest")]
#[cfg_attr(feature = "__doctest", cfg(doctest))]
#[macro_use]
extern crate doc_comment;
#[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
extern crate js_sys;
#[cfg(feature = "unstable-locales")]
extern crate pure_rust_locales;
#[cfg(feature = "bench")]
extern crate test;
#[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
extern crate wasm_bindgen;

#[cfg(feature = "__doctest")]
#[cfg_attr(feature = "__doctest", cfg(doctest))]
doctest!("../README.md");

// this reexport is to aid the transition and should not be in the prelude!
pub use oldtime::Duration;

pub use date::{Date, MAX_DATE, MIN_DATE};
#[cfg(feature = "rustc-serialize")]
pub use datetime::rustc_serialize::TsSeconds;
pub use datetime::{DateTime, SecondsFormat, MAX_DATETIME, MIN_DATETIME};
/// L10n locales.
#[cfg(feature = "unstable-locales")]
pub use format::Locale;
pub use format::{ParseError, ParseResult};
#[doc(no_inline)]
pub use naive::{IsoWeek, NaiveDate, NaiveDateTime, NaiveTime};
#[cfg(feature = "clock")]
#[doc(no_inline)]
pub use offset::Local;
#[doc(no_inline)]
pub use offset::{FixedOffset, LocalResult, Offset, TimeZone, Utc};
pub use round::{DurationRound, RoundingError, SubsecRound};

/// A convenience module appropriate for glob imports (`use chrono::prelude::*;`).
pub mod prelude {
    #[doc(no_inline)]
    pub use Date;
    #[cfg(feature = "clock")]
    #[doc(no_inline)]
    pub use Local;
    #[cfg(feature = "unstable-locales")]
    #[doc(no_inline)]
    pub use Locale;
    #[doc(no_inline)]
    pub use SubsecRound;
    #[doc(no_inline)]
    pub use {DateTime, SecondsFormat};
    #[doc(no_inline)]
    pub use {Datelike, Month, Timelike, Weekday};
    #[doc(no_inline)]
    pub use {FixedOffset, Utc};
    #[doc(no_inline)]
    pub use {NaiveDate, NaiveDateTime, NaiveTime};
    #[doc(no_inline)]
    pub use {Offset, TimeZone};
}

// useful throughout the codebase
macro_rules! try_opt {
    ($e:expr) => {
        match $e {
            Some(v) => v,
            None => return None,
        }
    };
}

mod div;
pub mod offset;
pub mod naive {
    //! Date and time types unconcerned with timezones.
    //!
    //! They are primarily building blocks for other types
    //! (e.g. [`TimeZone`](../offset/trait.TimeZone.html)),
    //! but can be also used for the simpler date and time handling.

    mod date;
    mod datetime;
    mod internals;
    mod isoweek;
    mod time;

    pub use self::date::{NaiveDate, MAX_DATE, MIN_DATE};
    #[cfg(feature = "rustc-serialize")]
    #[allow(deprecated)]
    pub use self::datetime::rustc_serialize::TsSeconds;
    pub use self::datetime::{NaiveDateTime, MAX_DATETIME, MIN_DATETIME};
    pub use self::isoweek::IsoWeek;
    pub use self::time::NaiveTime;

    #[cfg(feature = "__internal_bench")]
    #[doc(hidden)]
    pub use self::internals::YearFlags as __BenchYearFlags;

    /// Serialization/Deserialization of naive types in alternate formats
    ///
    /// The various modules in here are intended to be used with serde's [`with`
    /// annotation][1] to serialize as something other than the default [RFC
    /// 3339][2] format.
    ///
    /// [1]: https://serde.rs/attributes.html#field-attributes
    /// [2]: https://tools.ietf.org/html/rfc3339
    #[cfg(feature = "serde")]
    pub mod serde {
        pub use super::datetime::serde::*;
    }
}
mod date;
mod datetime;
pub mod format;
mod round;

#[cfg(feature = "__internal_bench")]
#[doc(hidden)]
pub use naive::__BenchYearFlags;

/// Serialization/Deserialization in alternate formats
///
/// The various modules in here are intended to be used with serde's [`with`
/// annotation][1] to serialize as something other than the default [RFC
/// 3339][2] format.
///
/// [1]: https://serde.rs/attributes.html#field-attributes
/// [2]: https://tools.ietf.org/html/rfc3339
#[cfg(feature = "serde")]
pub mod serde {
    pub use super::datetime::serde::*;
}

// Until rust 1.18 there  is no "pub(crate)" so to share this we need it in the root

#[cfg(feature = "serde")]
enum SerdeError<V: fmt::Display, D: fmt::Display> {
    NonExistent { timestamp: V },
    Ambiguous { timestamp: V, min: D, max: D },
}

/// Construct a [`SerdeError::NonExistent`]
#[cfg(feature = "serde")]
fn ne_timestamp<T: fmt::Display>(ts: T) -> SerdeError<T, u8> {
    SerdeError::NonExistent::<T, u8> { timestamp: ts }
}

#[cfg(feature = "serde")]
impl<V: fmt::Display, D: fmt::Display> fmt::Debug for SerdeError<V, D> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "ChronoSerdeError({})", self)
    }
}

// impl<V: fmt::Display, D: fmt::Debug> core::error::Error for SerdeError<V, D> {}
#[cfg(feature = "serde")]
impl<V: fmt::Display, D: fmt::Display> fmt::Display for SerdeError<V, D> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            &SerdeError::NonExistent { ref timestamp } => {
                write!(f, "value is not a legal timestamp: {}", timestamp)
            }
            &SerdeError::Ambiguous { ref timestamp, ref min, ref max } => write!(
                f,
                "value is an ambiguous timestamp: {}, could be either of {}, {}",
                timestamp, min, max
            ),
        }
    }
}

/// The day of week.
///
/// The order of the days of week depends on the context.
/// (This is why this type does *not* implement `PartialOrd` or `Ord` traits.)
/// One should prefer `*_from_monday` or `*_from_sunday` methods to get the correct result.
#[derive(PartialEq, Eq, Copy, Clone, Debug, Hash)]
#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
pub enum Weekday {
    /// Monday.
    Mon = 0,
    /// Tuesday.
    Tue = 1,
    /// Wednesday.
    Wed = 2,
    /// Thursday.
    Thu = 3,
    /// Friday.
    Fri = 4,
    /// Saturday.
    Sat = 5,
    /// Sunday.
    Sun = 6,
}

impl Weekday {
    /// The next day in the week.
    ///
    /// `w`:        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// ----------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.succ()`: | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun` | `Mon`
    #[inline]
    pub fn succ(&self) -> Weekday {
        match *self {
            Weekday::Mon => Weekday::Tue,
            Weekday::Tue => Weekday::Wed,
            Weekday::Wed => Weekday::Thu,
            Weekday::Thu => Weekday::Fri,
            Weekday::Fri => Weekday::Sat,
            Weekday::Sat => Weekday::Sun,
            Weekday::Sun => Weekday::Mon,
        }
    }

    /// The previous day in the week.
    ///
    /// `w`:        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// ----------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.pred()`: | `Sun` | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat`
    #[inline]
    pub fn pred(&self) -> Weekday {
        match *self {
            Weekday::Mon => Weekday::Sun,
            Weekday::Tue => Weekday::Mon,
            Weekday::Wed => Weekday::Tue,
            Weekday::Thu => Weekday::Wed,
            Weekday::Fri => Weekday::Thu,
            Weekday::Sat => Weekday::Fri,
            Weekday::Sun => Weekday::Sat,
        }
    }

    /// Returns a day-of-week number starting from Monday = 1. (ISO 8601 weekday number)
    ///
    /// `w`:                      | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// ------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.number_from_monday()`: | 1     | 2     | 3     | 4     | 5     | 6     | 7
    #[inline]
    pub fn number_from_monday(&self) -> u32 {
        match *self {
            Weekday::Mon => 1,
            Weekday::Tue => 2,
            Weekday::Wed => 3,
            Weekday::Thu => 4,
            Weekday::Fri => 5,
            Weekday::Sat => 6,
            Weekday::Sun => 7,
        }
    }

    /// Returns a day-of-week number starting from Sunday = 1.
    ///
    /// `w`:                      | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// ------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.number_from_sunday()`: | 2     | 3     | 4     | 5     | 6     | 7     | 1
    #[inline]
    pub fn number_from_sunday(&self) -> u32 {
        match *self {
            Weekday::Mon => 2,
            Weekday::Tue => 3,
            Weekday::Wed => 4,
            Weekday::Thu => 5,
            Weekday::Fri => 6,
            Weekday::Sat => 7,
            Weekday::Sun => 1,
        }
    }

    /// Returns a day-of-week number starting from Monday = 0.
    ///
    /// `w`:                        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// --------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.num_days_from_monday()`: | 0     | 1     | 2     | 3     | 4     | 5     | 6
    #[inline]
    pub fn num_days_from_monday(&self) -> u32 {
        match *self {
            Weekday::Mon => 0,
            Weekday::Tue => 1,
            Weekday::Wed => 2,
            Weekday::Thu => 3,
            Weekday::Fri => 4,
            Weekday::Sat => 5,
            Weekday::Sun => 6,
        }
    }

    /// Returns a day-of-week number starting from Sunday = 0.
    ///
    /// `w`:                        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
    /// --------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
    /// `w.num_days_from_sunday()`: | 1     | 2     | 3     | 4     | 5     | 6     | 0
    #[inline]
    pub fn num_days_from_sunday(&self) -> u32 {
        match *self {
            Weekday::Mon => 1,
            Weekday::Tue => 2,
            Weekday::Wed => 3,
            Weekday::Thu => 4,
            Weekday::Fri => 5,
            Weekday::Sat => 6,
            Weekday::Sun => 0,
        }
    }
}

impl fmt::Display for Weekday {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(match *self {
            Weekday::Mon => "Mon",
            Weekday::Tue => "Tue",
            Weekday::Wed => "Wed",
            Weekday::Thu => "Thu",
            Weekday::Fri => "Fri",
            Weekday::Sat => "Sat",
            Weekday::Sun => "Sun",
        })
    }
}

/// Any weekday can be represented as an integer from 0 to 6, which equals to
/// [`Weekday::num_days_from_monday`](#method.num_days_from_monday) in this implementation.
/// Do not heavily depend on this though; use explicit methods whenever possible.
impl num_traits::FromPrimitive for Weekday {
    #[inline]
    fn from_i64(n: i64) -> Option<Weekday> {
        match n {
            0 => Some(Weekday::Mon),
            1 => Some(Weekday::Tue),
            2 => Some(Weekday::Wed),
            3 => Some(Weekday::Thu),
            4 => Some(Weekday::Fri),
            5 => Some(Weekday::Sat),
            6 => Some(Weekday::Sun),
            _ => None,
        }
    }

    #[inline]
    fn from_u64(n: u64) -> Option<Weekday> {
        match n {
            0 => Some(Weekday::Mon),
            1 => Some(Weekday::Tue),
            2 => Some(Weekday::Wed),
            3 => Some(Weekday::Thu),
            4 => Some(Weekday::Fri),
            5 => Some(Weekday::Sat),
            6 => Some(Weekday::Sun),
            _ => None,
        }
    }
}

use core::fmt;

/// An error resulting from reading `Weekday` value with `FromStr`.
#[derive(Clone, PartialEq)]
pub struct ParseWeekdayError {
    _dummy: (),
}

impl fmt::Debug for ParseWeekdayError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "ParseWeekdayError {{ .. }}")
    }
}

// the actual `FromStr` implementation is in the `format` module to leverage the existing code

#[cfg(feature = "serde")]
mod weekday_serde {
    use super::Weekday;
    use core::fmt;
    use serdelib::{de, ser};

    impl ser::Serialize for Weekday {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: ser::Serializer,
        {
            serializer.collect_str(&self)
        }
    }

    struct WeekdayVisitor;

    impl<'de> de::Visitor<'de> for WeekdayVisitor {
        type Value = Weekday;

        fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "Weekday")
        }

        fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            value.parse().map_err(|_| E::custom("short or long weekday names expected"))
        }
    }

    impl<'de> de::Deserialize<'de> for Weekday {
        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            deserializer.deserialize_str(WeekdayVisitor)
        }
    }

    #[cfg(test)]
    extern crate serde_json;

    #[test]
    fn test_serde_serialize() {
        use self::serde_json::to_string;
        use Weekday::*;

        let cases: Vec<(Weekday, &str)> = vec![
            (Mon, "\"Mon\""),
            (Tue, "\"Tue\""),
            (Wed, "\"Wed\""),
            (Thu, "\"Thu\""),
            (Fri, "\"Fri\""),
            (Sat, "\"Sat\""),
            (Sun, "\"Sun\""),
        ];

        for (weekday, expected_str) in cases {
            let string = to_string(&weekday).unwrap();
            assert_eq!(string, expected_str);
        }
    }

    #[test]
    fn test_serde_deserialize() {
        use self::serde_json::from_str;
        use Weekday::*;

        let cases: Vec<(&str, Weekday)> = vec![
            ("\"mon\"", Mon),
            ("\"MONDAY\"", Mon),
            ("\"MonDay\"", Mon),
            ("\"mOn\"", Mon),
            ("\"tue\"", Tue),
            ("\"tuesday\"", Tue),
            ("\"wed\"", Wed),
            ("\"wednesday\"", Wed),
            ("\"thu\"", Thu),
            ("\"thursday\"", Thu),
            ("\"fri\"", Fri),
            ("\"friday\"", Fri),
            ("\"sat\"", Sat),
            ("\"saturday\"", Sat),
            ("\"sun\"", Sun),
            ("\"sunday\"", Sun),
        ];

        for (str, expected_weekday) in cases {
            let weekday = from_str::<Weekday>(str).unwrap();
            assert_eq!(weekday, expected_weekday);
        }

        let errors: Vec<&str> =
            vec!["\"not a weekday\"", "\"monDAYs\"", "\"mond\"", "mon", "\"thur\"", "\"thurs\""];

        for str in errors {
            from_str::<Weekday>(str).unwrap_err();
        }
    }
}

/// The month of the year.
///
/// This enum is just a convenience implementation.
/// The month in dates created by DateLike objects does not return this enum.
///
/// It is possible to convert from a date to a month independently
/// ```
/// # extern crate num_traits;
/// use num_traits::FromPrimitive;
/// use chrono::prelude::*;
/// let date = Utc.ymd(2019, 10, 28).and_hms(9, 10, 11);
/// // `2019-10-28T09:10:11Z`
/// let month = Month::from_u32(date.month());
/// assert_eq!(month, Some(Month::October))
/// ```
/// Or from a Month to an integer usable by dates
/// ```
/// # use chrono::prelude::*;
/// let month = Month::January;
/// let dt = Utc.ymd(2019, month.number_from_month(), 28).and_hms(9, 10, 11);
/// assert_eq!((dt.year(), dt.month(), dt.day()), (2019, 1, 28));
/// ```
/// Allows mapping from and to month, from 1-January to 12-December.
/// Can be Serialized/Deserialized with serde
// Actual implementation is zero-indexed, API intended as 1-indexed for more intuitive behavior.
#[derive(PartialEq, Eq, Copy, Clone, Debug, Hash)]
#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
pub enum Month {
    /// January
    January = 0,
    /// February
    February = 1,
    /// March
    March = 2,
    /// April
    April = 3,
    /// May
    May = 4,
    /// June
    June = 5,
    /// July
    July = 6,
    /// August
    August = 7,
    /// September
    September = 8,
    /// October
    October = 9,
    /// November
    November = 10,
    /// December
    December = 11,
}

impl Month {
    /// The next month.
    ///
    /// `m`:        | `January`  | `February` | `...` | `December`
    /// ----------- | ---------  | ---------- | --- | ---------
    /// `m.succ()`: | `February` | `March`    | `...` | `January`
    #[inline]
    pub fn succ(&self) -> Month {
        match *self {
            Month::January => Month::February,
            Month::February => Month::March,
            Month::March => Month::April,
            Month::April => Month::May,
            Month::May => Month::June,
            Month::June => Month::July,
            Month::July => Month::August,
            Month::August => Month::September,
            Month::September => Month::October,
            Month::October => Month::November,
            Month::November => Month::December,
            Month::December => Month::January,
        }
    }

    /// The previous month.
    ///
    /// `m`:        | `January`  | `February` | `...` | `December`
    /// ----------- | ---------  | ---------- | --- | ---------
    /// `m.succ()`: | `December` | `January`  | `...` | `November`
    #[inline]
    pub fn pred(&self) -> Month {
        match *self {
            Month::January => Month::December,
            Month::February => Month::January,
            Month::March => Month::February,
            Month::April => Month::March,
            Month::May => Month::April,
            Month::June => Month::May,
            Month::July => Month::June,
            Month::August => Month::July,
            Month::September => Month::August,
            Month::October => Month::September,
            Month::November => Month::October,
            Month::December => Month::November,
        }
    }

    /// Returns a month-of-year number starting from January = 1.
    ///
    /// `m`:                     | `January` | `February` | `...` | `December`
    /// -------------------------| --------- | ---------- | --- | -----
    /// `m.number_from_month()`: | 1         | 2          | `...` | 12
    #[inline]
    pub fn number_from_month(&self) -> u32 {
        match *self {
            Month::January => 1,
            Month::February => 2,
            Month::March => 3,
            Month::April => 4,
            Month::May => 5,
            Month::June => 6,
            Month::July => 7,
            Month::August => 8,
            Month::September => 9,
            Month::October => 10,
            Month::November => 11,
            Month::December => 12,
        }
    }

    /// Get the name of the month
    ///
    /// ```
    /// use chrono::Month;
    ///
    /// assert_eq!(Month::January.name(), "January")
    /// ```
    pub fn name(&self) -> &'static str {
        match *self {
            Month::January => "January",
            Month::February => "February",
            Month::March => "March",
            Month::April => "April",
            Month::May => "May",
            Month::June => "June",
            Month::July => "July",
            Month::August => "August",
            Month::September => "September",
            Month::October => "October",
            Month::November => "November",
            Month::December => "December",
        }
    }
}

impl num_traits::FromPrimitive for Month {
    /// Returns an Option<Month> from a i64, assuming a 1-index, January = 1.
    ///
    /// `Month::from_i64(n: i64)`: | `1`                  | `2`                   | ... | `12`
    /// ---------------------------| -------------------- | --------------------- | ... | -----
    /// ``:                        | Some(Month::January) | Some(Month::February) | ... | Some(Month::December)

    #[inline]
    fn from_u64(n: u64) -> Option<Month> {
        Self::from_u32(n as u32)
    }

    #[inline]
    fn from_i64(n: i64) -> Option<Month> {
        Self::from_u32(n as u32)
    }

    #[inline]
    fn from_u32(n: u32) -> Option<Month> {
        match n {
            1 => Some(Month::January),
            2 => Some(Month::February),
            3 => Some(Month::March),
            4 => Some(Month::April),
            5 => Some(Month::May),
            6 => Some(Month::June),
            7 => Some(Month::July),
            8 => Some(Month::August),
            9 => Some(Month::September),
            10 => Some(Month::October),
            11 => Some(Month::November),
            12 => Some(Month::December),
            _ => None,
        }
    }
}

/// An error resulting from reading `<Month>` value with `FromStr`.
#[derive(Clone, PartialEq)]
pub struct ParseMonthError {
    _dummy: (),
}

impl fmt::Debug for ParseMonthError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "ParseMonthError {{ .. }}")
    }
}

#[cfg(feature = "serde")]
mod month_serde {
    use super::Month;
    use serdelib::{de, ser};

    use core::fmt;

    impl ser::Serialize for Month {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: ser::Serializer,
        {
            serializer.collect_str(self.name())
        }
    }

    struct MonthVisitor;

    impl<'de> de::Visitor<'de> for MonthVisitor {
        type Value = Month;

        fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "Month")
        }

        fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            value.parse().map_err(|_| E::custom("short (3-letter) or full month names expected"))
        }
    }

    impl<'de> de::Deserialize<'de> for Month {
        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            deserializer.deserialize_str(MonthVisitor)
        }
    }

    #[cfg(test)]
    extern crate serde_json;

    #[test]
    fn test_serde_serialize() {
        use self::serde_json::to_string;
        use Month::*;

        let cases: Vec<(Month, &str)> = vec![
            (January, "\"January\""),
            (February, "\"February\""),
            (March, "\"March\""),
            (April, "\"April\""),
            (May, "\"May\""),
            (June, "\"June\""),
            (July, "\"July\""),
            (August, "\"August\""),
            (September, "\"September\""),
            (October, "\"October\""),
            (November, "\"November\""),
            (December, "\"December\""),
        ];

        for (month, expected_str) in cases {
            let string = to_string(&month).unwrap();
            assert_eq!(string, expected_str);
        }
    }

    #[test]
    fn test_serde_deserialize() {
        use self::serde_json::from_str;
        use Month::*;

        let cases: Vec<(&str, Month)> = vec![
            ("\"january\"", January),
            ("\"jan\"", January),
            ("\"FeB\"", February),
            ("\"MAR\"", March),
            ("\"mar\"", March),
            ("\"april\"", April),
            ("\"may\"", May),
            ("\"june\"", June),
            ("\"JULY\"", July),
            ("\"august\"", August),
            ("\"september\"", September),
            ("\"October\"", October),
            ("\"November\"", November),
            ("\"DECEmbEr\"", December),
        ];

        for (string, expected_month) in cases {
            let month = from_str::<Month>(string).unwrap();
            assert_eq!(month, expected_month);
        }

        let errors: Vec<&str> =
            vec!["\"not a month\"", "\"ja\"", "\"Dece\"", "Dec", "\"Augustin\""];

        for string in errors {
            from_str::<Month>(string).unwrap_err();
        }
    }
}

/// The common set of methods for date component.
pub trait Datelike: Sized {
    /// Returns the year number in the [calendar date](./naive/struct.NaiveDate.html#calendar-date).
    fn year(&self) -> i32;

    /// Returns the absolute year number starting from 1 with a boolean flag,
    /// which is false when the year predates the epoch (BCE/BC) and true otherwise (CE/AD).
    #[inline]
    fn year_ce(&self) -> (bool, u32) {
        let year = self.year();
        if year < 1 {
            (false, (1 - year) as u32)
        } else {
            (true, year as u32)
        }
    }

    /// Returns the month number starting from 1.
    ///
    /// The return value ranges from 1 to 12.
    fn month(&self) -> u32;

    /// Returns the month number starting from 0.
    ///
    /// The return value ranges from 0 to 11.
    fn month0(&self) -> u32;

    /// Returns the day of month starting from 1.
    ///
    /// The return value ranges from 1 to 31. (The last day of month differs by months.)
    fn day(&self) -> u32;

    /// Returns the day of month starting from 0.
    ///
    /// The return value ranges from 0 to 30. (The last day of month differs by months.)
    fn day0(&self) -> u32;

    /// Returns the day of year starting from 1.
    ///
    /// The return value ranges from 1 to 366. (The last day of year differs by years.)
    fn ordinal(&self) -> u32;

    /// Returns the day of year starting from 0.
    ///
    /// The return value ranges from 0 to 365. (The last day of year differs by years.)
    fn ordinal0(&self) -> u32;

    /// Returns the day of week.
    fn weekday(&self) -> Weekday;

    /// Returns the ISO week.
    fn iso_week(&self) -> IsoWeek;

    /// Makes a new value with the year number changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_year(&self, year: i32) -> Option<Self>;

    /// Makes a new value with the month number (starting from 1) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_month(&self, month: u32) -> Option<Self>;

    /// Makes a new value with the month number (starting from 0) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_month0(&self, month0: u32) -> Option<Self>;

    /// Makes a new value with the day of month (starting from 1) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_day(&self, day: u32) -> Option<Self>;

    /// Makes a new value with the day of month (starting from 0) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_day0(&self, day0: u32) -> Option<Self>;

    /// Makes a new value with the day of year (starting from 1) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_ordinal(&self, ordinal: u32) -> Option<Self>;

    /// Makes a new value with the day of year (starting from 0) changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_ordinal0(&self, ordinal0: u32) -> Option<Self>;

    /// Counts the days in the proleptic Gregorian calendar, with January 1, Year 1 (CE) as day 1.
    ///
    /// # Examples
    ///
    /// ```
    /// use chrono::{NaiveDate, Datelike};
    ///
    /// assert_eq!(NaiveDate::from_ymd(1970, 1, 1).num_days_from_ce(), 719_163);
    /// assert_eq!(NaiveDate::from_ymd(2, 1, 1).num_days_from_ce(), 366);
    /// assert_eq!(NaiveDate::from_ymd(1, 1, 1).num_days_from_ce(), 1);
    /// assert_eq!(NaiveDate::from_ymd(0, 1, 1).num_days_from_ce(), -365);
    /// ```
    fn num_days_from_ce(&self) -> i32 {
        // See test_num_days_from_ce_against_alternative_impl below for a more straightforward
        // implementation.

        // we know this wouldn't overflow since year is limited to 1/2^13 of i32's full range.
        let mut year = self.year() - 1;
        let mut ndays = 0;
        if year < 0 {
            let excess = 1 + (-year) / 400;
            year += excess * 400;
            ndays -= excess * 146_097;
        }
        let div_100 = year / 100;
        ndays += ((year * 1461) >> 2) - div_100 + (div_100 >> 2);
        ndays + self.ordinal() as i32
    }
}

/// The common set of methods for time component.
pub trait Timelike: Sized {
    /// Returns the hour number from 0 to 23.
    fn hour(&self) -> u32;

    /// Returns the hour number from 1 to 12 with a boolean flag,
    /// which is false for AM and true for PM.
    #[inline]
    fn hour12(&self) -> (bool, u32) {
        let hour = self.hour();
        let mut hour12 = hour % 12;
        if hour12 == 0 {
            hour12 = 12;
        }
        (hour >= 12, hour12)
    }

    /// Returns the minute number from 0 to 59.
    fn minute(&self) -> u32;

    /// Returns the second number from 0 to 59.
    fn second(&self) -> u32;

    /// Returns the number of nanoseconds since the whole non-leap second.
    /// The range from 1,000,000,000 to 1,999,999,999 represents
    /// the [leap second](./naive/struct.NaiveTime.html#leap-second-handling).
    fn nanosecond(&self) -> u32;

    /// Makes a new value with the hour number changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_hour(&self, hour: u32) -> Option<Self>;

    /// Makes a new value with the minute number changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    fn with_minute(&self, min: u32) -> Option<Self>;

    /// Makes a new value with the second number changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    /// As with the [`second`](#tymethod.second) method,
    /// the input range is restricted to 0 through 59.
    fn with_second(&self, sec: u32) -> Option<Self>;

    /// Makes a new value with nanoseconds since the whole non-leap second changed.
    ///
    /// Returns `None` when the resulting value would be invalid.
    /// As with the [`nanosecond`](#tymethod.nanosecond) method,
    /// the input range can exceed 1,000,000,000 for leap seconds.
    fn with_nanosecond(&self, nano: u32) -> Option<Self>;

    /// Returns the number of non-leap seconds past the last midnight.
    #[inline]
    fn num_seconds_from_midnight(&self) -> u32 {
        self.hour() * 3600 + self.minute() * 60 + self.second()
    }
}

#[cfg(test)]
extern crate num_iter;

mod test {
    #[allow(unused_imports)]
    use super::*;

    #[test]
    fn test_readme_doomsday() {
        use num_iter::range_inclusive;

        for y in range_inclusive(naive::MIN_DATE.year(), naive::MAX_DATE.year()) {
            // even months
            let d4 = NaiveDate::from_ymd(y, 4, 4);
            let d6 = NaiveDate::from_ymd(y, 6, 6);
            let d8 = NaiveDate::from_ymd(y, 8, 8);
            let d10 = NaiveDate::from_ymd(y, 10, 10);
            let d12 = NaiveDate::from_ymd(y, 12, 12);

            // nine to five, seven-eleven
            let d59 = NaiveDate::from_ymd(y, 5, 9);
            let d95 = NaiveDate::from_ymd(y, 9, 5);
            let d711 = NaiveDate::from_ymd(y, 7, 11);
            let d117 = NaiveDate::from_ymd(y, 11, 7);

            // "March 0"
            let d30 = NaiveDate::from_ymd(y, 3, 1).pred();

            let weekday = d30.weekday();
            let other_dates = [d4, d6, d8, d10, d12, d59, d95, d711, d117];
            assert!(other_dates.iter().all(|d| d.weekday() == weekday));
        }
    }

    #[test]
    fn test_month_enum_primitive_parse() {
        use num_traits::FromPrimitive;

        let jan_opt = Month::from_u32(1);
        let feb_opt = Month::from_u64(2);
        let dec_opt = Month::from_i64(12);
        let no_month = Month::from_u32(13);
        assert_eq!(jan_opt, Some(Month::January));
        assert_eq!(feb_opt, Some(Month::February));
        assert_eq!(dec_opt, Some(Month::December));
        assert_eq!(no_month, None);

        let date = Utc.ymd(2019, 10, 28).and_hms(9, 10, 11);
        assert_eq!(Month::from_u32(date.month()), Some(Month::October));

        let month = Month::January;
        let dt = Utc.ymd(2019, month.number_from_month(), 28).and_hms(9, 10, 11);
        assert_eq!((dt.year(), dt.month(), dt.day()), (2019, 1, 28));
    }
}

/// Tests `Datelike::num_days_from_ce` against an alternative implementation.
///
/// The alternative implementation is not as short as the current one but it is simpler to
/// understand, with less unexplained magic constants.
#[test]
fn test_num_days_from_ce_against_alternative_impl() {
    /// Returns the number of multiples of `div` in the range `start..end`.
    ///
    /// If the range `start..end` is back-to-front, i.e. `start` is greater than `end`, the
    /// behaviour is defined by the following equation:
    /// `in_between(start, end, div) == - in_between(end, start, div)`.
    ///
    /// When `div` is 1, this is equivalent to `end - start`, i.e. the length of `start..end`.
    ///
    /// # Panics
    ///
    /// Panics if `div` is not positive.
    fn in_between(start: i32, end: i32, div: i32) -> i32 {
        assert!(div > 0, "in_between: nonpositive div = {}", div);
        let start = (start.div_euclid(div), start.rem_euclid(div));
        let end = (end.div_euclid(div), end.rem_euclid(div));
        // The lowest multiple of `div` greater than or equal to `start`, divided.
        let start = start.0 + (start.1 != 0) as i32;
        // The lowest multiple of `div` greater than or equal to   `end`, divided.
        let end = end.0 + (end.1 != 0) as i32;
        end - start
    }

    /// Alternative implementation to `Datelike::num_days_from_ce`
    fn num_days_from_ce<Date: Datelike>(date: &Date) -> i32 {
        let year = date.year();
        let diff = move |div| in_between(1, year, div);
        // 365 days a year, one more in leap years. In the gregorian calendar, leap years are all
        // the multiples of 4 except multiples of 100 but including multiples of 400.
        date.ordinal() as i32 + 365 * diff(1) + diff(4) - diff(100) + diff(400)
    }

    use num_iter::range_inclusive;

    for year in range_inclusive(naive::MIN_DATE.year(), naive::MAX_DATE.year()) {
        let jan1_year = NaiveDate::from_ymd(year, 1, 1);
        assert_eq!(
            jan1_year.num_days_from_ce(),
            num_days_from_ce(&jan1_year),
            "on {:?}",
            jan1_year
        );
        let mid_year = jan1_year + Duration::days(133);
        assert_eq!(mid_year.num_days_from_ce(), num_days_from_ce(&mid_year), "on {:?}", mid_year);
    }
}

#[test]
fn test_month_enum_succ_pred() {
    assert_eq!(Month::January.succ(), Month::February);
    assert_eq!(Month::December.succ(), Month::January);
    assert_eq!(Month::January.pred(), Month::December);
    assert_eq!(Month::February.pred(), Month::January);
}