Is it possible to calculate a local date from a UTC time representing a local midnight?
想象一下你在某个时区(例如America / New_York)采取当地日期,比如2016-12-28,并将该日期的开头转换为UTC(在本例中为2016-12-28T05:00:00Z)。
那么从那个UTC时间开始可以在不知道时区的情况下回到原始的本地日期吗? 所有你知道的是UTC时间代表当地的一些午夜/一天的开始。
我想在某些情况下这是可能的,例如 当偏移量相当小时,但我不确定时区接近日期线时是否会有两个可能的答案,即当两个时区具有相同的时间但是日期/偏移不同时(-10) 和+14)。
(此问题最初是在数据库中遇到的,其中本地日期错误地存储在UTC中,并且原始时区数据难以再次检索。)
在某些约束下,可以识别时区偏移(
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您给出了一个非常明确的案例,说明如何无法确定国际日期变更线附近的抵消日期。
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例如,考虑
2016-12-31T10:00:00Z 。那可能是2016-12-31T00:00:00-10:00 (可能是Pacific/Honolulu ),或者可能是2017-01-01T00:00:00+14:00 (可能是Pacific/Tongatapu )。 -
-10/+14 和-11/+13 两种配对都是可能的,但地球上没有居住的地方实际上使用-12 。因此,如果您的价值恰好在正午时间,那么它们可能+12 ,除非您正在与海上船舶打交道。
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您期望的时区中可能不存在本地午夜值。
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例如,
2016-10-16T03:00:00Z 是America/Sao_Paulo 和America/Bahia (都在巴西)的一天的开始。但是,America/Sao_Paulo 的本地时间01:00 ,而不是00:00 。由于他们的DST春季前进过渡,当天没有午夜。
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例如,
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本地午夜值可能在您期望的时区中存在两次。
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例如,在
America/Havana 中,由于它们的DST回退转换,2016-11-06T04:00:00Z 和2016-11-06T05:00:00Z 都具有00:00 的本地时间。
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例如,在
因此,在一般情况下,您可以将其中大部分恢复到原始偏移量,但对于具有
使用这个免费的开源C ++库,我可以计算出这个问题的可能时区列表。
更新我已经重写了此代码的驱动程序,以便真正探索一整天的结果,并将其与Matt优秀答案中的具体示例进行比较。
这是代码:
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 | #include <iostream> #include <vector> template <class Duration> std::vector<date::zoned_time<std::common_type_t<Duration, std::chrono::seconds>>> find_by_offset(date::sys_time<Duration> tp, const std::chrono::seconds& offset) { using namespace std::chrono; using namespace date; std::vector<zoned_time<std::common_type_t<Duration, std::chrono::seconds>>> results; auto& db = get_tzdb(); for (auto& z : db.zones) { if (z.get_info(tp).offset == offset) results.push_back(make_zoned(&z, tp)); } return results; } int main() { using namespace date; using namespace std::chrono; for (auto offset = -15h; offset <= 13h; offset += 1h) { auto tp = sys_days{2016_y/12/28} + offset; std::cout <<"These are all the timezones it is midnight at" << format("%F %T %Z ", tp); auto d0 = round<days>(tp); auto dm1 = d0 - days{1}; auto dp1 = d0 + days{1}; auto v = find_by_offset(tp, dm1 - tp); for (auto const& zt : v) std::cout << format("%F %T %Z %z", zt) << zt.get_time_zone()->name() << ' '; v = find_by_offset(tp, d0 - tp); for (auto const& zt : v) std::cout << format("%F %T %Z %z", zt) << zt.get_time_zone()->name() << ' '; v = find_by_offset(tp, dp1 - tp); for (auto const& zt : v) std::cout << format("%F %T %Z %z", zt) << zt.get_time_zone()->name() << ' '; std::cout << ' '; } } |
该代码创建一个UTC时间戳和偏移对,并将其提供给
以下是2016-12-28日期可能有午夜的所有结果:
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 | These are all the timezones it is midnight at 2016-12-27 09:00:00 UTC 2016-12-27 00:00:00 AKST -0900 America/Anchorage 2016-12-27 00:00:00 AKST -0900 America/Juneau 2016-12-27 00:00:00 AKST -0900 America/Metlakatla 2016-12-27 00:00:00 AKST -0900 America/Nome 2016-12-27 00:00:00 AKST -0900 America/Sitka 2016-12-27 00:00:00 AKST -0900 America/Yakutat 2016-12-27 00:00:00 -09 -0900 Etc/GMT+9 2016-12-27 00:00:00 GAMT -0900 Pacific/Gambier These are all the timezones it is midnight at 2016-12-27 10:00:00 UTC 2016-12-27 00:00:00 HST -1000 America/Adak 2016-12-27 00:00:00 -10 -1000 Etc/GMT+10 2016-12-27 00:00:00 HST -1000 HST 2016-12-27 00:00:00 HST -1000 Pacific/Honolulu 2016-12-27 00:00:00 CKT -1000 Pacific/Rarotonga 2016-12-27 00:00:00 TAHT -1000 Pacific/Tahiti 2016-12-28 00:00:00 +14 +1400 Etc/GMT-14 2016-12-28 00:00:00 WSDT +1400 Pacific/Apia 2016-12-28 00:00:00 LINT +1400 Pacific/Kiritimati 2016-12-28 00:00:00 +14 +1400 Pacific/Tongatapu These are all the timezones it is midnight at 2016-12-27 11:00:00 UTC 2016-12-27 00:00:00 -11 -1100 Etc/GMT+11 2016-12-27 00:00:00 NUT -1100 Pacific/Niue 2016-12-27 00:00:00 SST -1100 Pacific/Pago_Pago 2016-12-28 00:00:00 +13 +1300 Etc/GMT-13 2016-12-28 00:00:00 NZDT +1300 Pacific/Auckland 2016-12-28 00:00:00 PHOT +1300 Pacific/Enderbury 2016-12-28 00:00:00 TKT +1300 Pacific/Fakaofo 2016-12-28 00:00:00 FJST +1300 Pacific/Fiji These are all the timezones it is midnight at 2016-12-27 12:00:00 UTC 2016-12-27 00:00:00 -12 -1200 Etc/GMT+12 2016-12-28 00:00:00 +12 +1200 Asia/Anadyr 2016-12-28 00:00:00 +12 +1200 Asia/Kamchatka 2016-12-28 00:00:00 +12 +1200 Etc/GMT-12 2016-12-28 00:00:00 TVT +1200 Pacific/Funafuti 2016-12-28 00:00:00 MHT +1200 Pacific/Kwajalein 2016-12-28 00:00:00 MHT +1200 Pacific/Majuro 2016-12-28 00:00:00 NRT +1200 Pacific/Nauru 2016-12-28 00:00:00 GILT +1200 Pacific/Tarawa 2016-12-28 00:00:00 WAKT +1200 Pacific/Wake 2016-12-28 00:00:00 WFT +1200 Pacific/Wallis These are all the timezones it is midnight at 2016-12-27 13:00:00 UTC 2016-12-28 00:00:00 +11 +1100 Antarctica/Casey 2016-12-28 00:00:00 MIST +1100 Antarctica/Macquarie 2016-12-28 00:00:00 +11 +1100 Asia/Magadan 2016-12-28 00:00:00 +11 +1100 Asia/Sakhalin 2016-12-28 00:00:00 +11 +1100 Asia/Srednekolymsk 2016-12-28 00:00:00 AEDT +1100 Australia/Currie 2016-12-28 00:00:00 AEDT +1100 Australia/Hobart 2016-12-28 00:00:00 LHDT +1100 Australia/Lord_Howe 2016-12-28 00:00:00 AEDT +1100 Australia/Melbourne 2016-12-28 00:00:00 AEDT +1100 Australia/Sydney 2016-12-28 00:00:00 +11 +1100 Etc/GMT-11 2016-12-28 00:00:00 BST +1100 Pacific/Bougainville 2016-12-28 00:00:00 VUT +1100 Pacific/Efate 2016-12-28 00:00:00 SBT +1100 Pacific/Guadalcanal 2016-12-28 00:00:00 KOST +1100 Pacific/Kosrae 2016-12-28 00:00:00 NFT +1100 Pacific/Norfolk 2016-12-28 00:00:00 NCT +1100 Pacific/Noumea 2016-12-28 00:00:00 PONT +1100 Pacific/Pohnpei These are all the timezones it is midnight at 2016-12-27 14:00:00 UTC 2016-12-28 00:00:00 +10 +1000 Antarctica/DumontDUrville 2016-12-28 00:00:00 +10 +1000 Asia/Ust-Nera 2016-12-28 00:00:00 +10 +1000 Asia/Vladivostok 2016-12-28 00:00:00 AEST +1000 Australia/Brisbane 2016-12-28 00:00:00 AEST +1000 Australia/Lindeman 2016-12-28 00:00:00 +10 +1000 Etc/GMT-10 2016-12-28 00:00:00 CHUT +1000 Pacific/Chuuk 2016-12-28 00:00:00 ChST +1000 Pacific/Guam 2016-12-28 00:00:00 PGT +1000 Pacific/Port_Moresby These are all the timezones it is midnight at 2016-12-27 15:00:00 UTC 2016-12-28 00:00:00 +09 +0900 Asia/Chita 2016-12-28 00:00:00 TLT +0900 Asia/Dili 2016-12-28 00:00:00 WIT +0900 Asia/Jayapura 2016-12-28 00:00:00 +09 +0900 Asia/Khandyga 2016-12-28 00:00:00 KST +0900 Asia/Seoul 2016-12-28 00:00:00 JST +0900 Asia/Tokyo 2016-12-28 00:00:00 +09 +0900 Asia/Yakutsk 2016-12-28 00:00:00 +09 +0900 Etc/GMT-9 2016-12-28 00:00:00 PWT +0900 Pacific/Palau These are all the timezones it is midnight at 2016-12-27 16:00:00 UTC 2016-12-28 00:00:00 BNT +0800 Asia/Brunei 2016-12-28 00:00:00 CHOT +0800 Asia/Choibalsan 2016-12-28 00:00:00 HKT +0800 Asia/Hong_Kong 2016-12-28 00:00:00 +08 +0800 Asia/Irkutsk 2016-12-28 00:00:00 MYT +0800 Asia/Kuala_Lumpur 2016-12-28 00:00:00 MYT +0800 Asia/Kuching 2016-12-28 00:00:00 CST +0800 Asia/Macau 2016-12-28 00:00:00 WITA +0800 Asia/Makassar 2016-12-28 00:00:00 PHT +0800 Asia/Manila 2016-12-28 00:00:00 CST +0800 Asia/Shanghai 2016-12-28 00:00:00 SGT +0800 Asia/Singapore 2016-12-28 00:00:00 CST +0800 Asia/Taipei 2016-12-28 00:00:00 ULAT +0800 Asia/Ulaanbaatar 2016-12-28 00:00:00 AWST +0800 Australia/Perth 2016-12-28 00:00:00 +08 +0800 Etc/GMT-8 These are all the timezones it is midnight at 2016-12-27 17:00:00 UTC 2016-12-28 00:00:00 +07 +0700 Antarctica/Davis 2016-12-28 00:00:00 ICT +0700 Asia/Bangkok 2016-12-28 00:00:00 +07 +0700 Asia/Barnaul 2016-12-28 00:00:00 ICT +0700 Asia/Ho_Chi_Minh 2016-12-28 00:00:00 HOVT +0700 Asia/Hovd 2016-12-28 00:00:00 WIB +0700 Asia/Jakarta 2016-12-28 00:00:00 +07 +0700 Asia/Krasnoyarsk 2016-12-28 00:00:00 +07 +0700 Asia/Novokuznetsk 2016-12-28 00:00:00 +07 +0700 Asia/Novosibirsk 2016-12-28 00:00:00 WIB +0700 Asia/Pontianak 2016-12-28 00:00:00 +07 +0700 Asia/Tomsk 2016-12-28 00:00:00 +07 +0700 Etc/GMT-7 2016-12-28 00:00:00 CXT +0700 Indian/Christmas These are all the timezones it is midnight at 2016-12-27 18:00:00 UTC 2016-12-28 00:00:00 +06 +0600 Antarctica/Vostok 2016-12-28 00:00:00 +06 +0600 Asia/Almaty 2016-12-28 00:00:00 +06 +0600 Asia/Bishkek 2016-12-28 00:00:00 BDT +0600 Asia/Dhaka 2016-12-28 00:00:00 +06 +0600 Asia/Omsk 2016-12-28 00:00:00 +06 +0600 Asia/Qyzylorda 2016-12-28 00:00:00 BTT +0600 Asia/Thimphu 2016-12-28 00:00:00 XJT +0600 Asia/Urumqi 2016-12-28 00:00:00 +06 +0600 Etc/GMT-6 2016-12-28 00:00:00 IOT +0600 Indian/Chagos These are all the timezones it is midnight at 2016-12-27 19:00:00 UTC 2016-12-28 00:00:00 +05 +0500 Antarctica/Mawson 2016-12-28 00:00:00 +05 +0500 Asia/Aqtau 2016-12-28 00:00:00 +05 +0500 Asia/Aqtobe 2016-12-28 00:00:00 +05 +0500 Asia/Ashgabat 2016-12-28 00:00:00 +05 +0500 Asia/Atyrau 2016-12-28 00:00:00 +05 +0500 Asia/Dushanbe 2016-12-28 00:00:00 PKT +0500 Asia/Karachi 2016-12-28 00:00:00 +05 +0500 Asia/Oral 2016-12-28 00:00:00 +05 +0500 Asia/Samarkand 2016-12-28 00:00:00 +05 +0500 Asia/Tashkent 2016-12-28 00:00:00 +05 +0500 Asia/Yekaterinburg 2016-12-28 00:00:00 +05 +0500 Etc/GMT-5 2016-12-28 00:00:00 +05 +0500 Indian/Kerguelen 2016-12-28 00:00:00 MVT +0500 Indian/Maldives These are all the timezones it is midnight at 2016-12-27 20:00:00 UTC 2016-12-28 00:00:00 +04 +0400 Asia/Baku 2016-12-28 00:00:00 GST +0400 Asia/Dubai 2016-12-28 00:00:00 +04 +0400 Asia/Tbilisi 2016-12-28 00:00:00 +04 +0400 Asia/Yerevan 2016-12-28 00:00:00 +04 +0400 Etc/GMT-4 2016-12-28 00:00:00 +04 +0400 Europe/Astrakhan 2016-12-28 00:00:00 +04 +0400 Europe/Samara 2016-12-28 00:00:00 +04 +0400 Europe/Saratov 2016-12-28 00:00:00 +04 +0400 Europe/Ulyanovsk 2016-12-28 00:00:00 SCT +0400 Indian/Mahe 2016-12-28 00:00:00 MUT +0400 Indian/Mauritius 2016-12-28 00:00:00 RET +0400 Indian/Reunion These are all the timezones it is midnight at 2016-12-27 21:00:00 UTC 2016-12-28 00:00:00 EAT +0300 Africa/Khartoum 2016-12-28 00:00:00 EAT +0300 Africa/Nairobi 2016-12-28 00:00:00 +03 +0300 Antarctica/Syowa 2016-12-28 00:00:00 AST +0300 Asia/Baghdad 2016-12-28 00:00:00 +03 +0300 Asia/Famagusta 2016-12-28 00:00:00 AST +0300 Asia/Qatar 2016-12-28 00:00:00 AST +0300 Asia/Riyadh 2016-12-28 00:00:00 +03 +0300 Etc/GMT-3 2016-12-28 00:00:00 +03 +0300 Europe/Istanbul 2016-12-28 00:00:00 +03 +0300 Europe/Kirov 2016-12-28 00:00:00 +03 +0300 Europe/Minsk 2016-12-28 00:00:00 MSK +0300 Europe/Moscow 2016-12-28 00:00:00 MSK +0300 Europe/Simferopol 2016-12-28 00:00:00 +03 +0300 Europe/Volgograd These are all the timezones it is midnight at 2016-12-27 22:00:00 UTC 2016-12-28 00:00:00 EET +0200 Africa/Cairo 2016-12-28 00:00:00 SAST +0200 Africa/Johannesburg 2016-12-28 00:00:00 CAT +0200 Africa/Maputo 2016-12-28 00:00:00 EET +0200 Africa/Tripoli 2016-12-28 00:00:00 WAST +0200 Africa/Windhoek 2016-12-28 00:00:00 EET +0200 Asia/Amman 2016-12-28 00:00:00 EET +0200 Asia/Beirut 2016-12-28 00:00:00 EET +0200 Asia/Damascus 2016-12-28 00:00:00 EET +0200 Asia/Gaza 2016-12-28 00:00:00 EET +0200 Asia/Hebron 2016-12-28 00:00:00 IST +0200 Asia/Jerusalem 2016-12-28 00:00:00 EET +0200 Asia/Nicosia 2016-12-28 00:00:00 EET +0200 EET 2016-12-28 00:00:00 +02 +0200 Etc/GMT-2 2016-12-28 00:00:00 EET +0200 Europe/Athens 2016-12-28 00:00:00 EET +0200 Europe/Bucharest 2016-12-28 00:00:00 EET +0200 Europe/Chisinau 2016-12-28 00:00:00 EET +0200 Europe/Helsinki 2016-12-28 00:00:00 EET +0200 Europe/Kaliningrad 2016-12-28 00:00:00 EET +0200 Europe/Kiev 2016-12-28 00:00:00 EET +0200 Europe/Riga 2016-12-28 00:00:00 EET +0200 Europe/Sofia 2016-12-28 00:00:00 EET +0200 Europe/Tallinn 2016-12-28 00:00:00 EET +0200 Europe/Uzhgorod 2016-12-28 00:00:00 EET +0200 Europe/Vilnius 2016-12-28 00:00:00 EET +0200 Europe/Zaporozhye These are all the timezones it is midnight at 2016-12-27 23:00:00 UTC 2016-12-28 00:00:00 CET +0100 Africa/Algiers 2016-12-28 00:00:00 CET +0100 Africa/Ceuta 2016-12-28 00:00:00 WAT +0100 Africa/Lagos 2016-12-28 00:00:00 WAT +0100 Africa/Ndjamena 2016-12-28 00:00:00 CET +0100 Africa/Tunis 2016-12-28 00:00:00 CET +0100 CET 2016-12-28 00:00:00 +01 +0100 Etc/GMT-1 2016-12-28 00:00:00 CET +0100 Europe/Amsterdam 2016-12-28 00:00:00 CET +0100 Europe/Andorra 2016-12-28 00:00:00 CET +0100 Europe/Belgrade 2016-12-28 00:00:00 CET +0100 Europe/Berlin 2016-12-28 00:00:00 CET +0100 Europe/Brussels 2016-12-28 00:00:00 CET +0100 Europe/Budapest 2016-12-28 00:00:00 CET +0100 Europe/Copenhagen 2016-12-28 00:00:00 CET +0100 Europe/Gibraltar 2016-12-28 00:00:00 CET +0100 Europe/Luxembourg 2016-12-28 00:00:00 CET +0100 Europe/Madrid 2016-12-28 00:00:00 CET +0100 Europe/Malta 2016-12-28 00:00:00 CET +0100 Europe/Monaco 2016-12-28 00:00:00 CET +0100 Europe/Oslo 2016-12-28 00:00:00 CET +0100 Europe/Paris 2016-12-28 00:00:00 CET +0100 Europe/Prague 2016-12-28 00:00:00 CET +0100 Europe/Rome 2016-12-28 00:00:00 CET +0100 Europe/Stockholm 2016-12-28 00:00:00 CET +0100 Europe/Tirane 2016-12-28 00:00:00 CET +0100 Europe/Vienna 2016-12-28 00:00:00 CET +0100 Europe/Warsaw 2016-12-28 00:00:00 CET +0100 Europe/Zurich 2016-12-28 00:00:00 MET +0100 MET These are all the timezones it is midnight at 2016-12-28 00:00:00 UTC 2016-12-28 00:00:00 GMT +0000 Africa/Abidjan 2016-12-28 00:00:00 GMT +0000 Africa/Accra 2016-12-28 00:00:00 GMT +0000 Africa/Bissau 2016-12-28 00:00:00 WET +0000 Africa/Casablanca 2016-12-28 00:00:00 WET +0000 Africa/El_Aaiun 2016-12-28 00:00:00 GMT +0000 Africa/Monrovia 2016-12-28 00:00:00 GMT +0000 America/Danmarkshavn 2016-12-28 00:00:00 +00 +0000 Antarctica/Troll 2016-12-28 00:00:00 WET +0000 Atlantic/Canary 2016-12-28 00:00:00 WET +0000 Atlantic/Faroe 2016-12-28 00:00:00 WET +0000 Atlantic/Madeira 2016-12-28 00:00:00 GMT +0000 Atlantic/Reykjavik 2016-12-28 00:00:00 GMT +0000 Etc/GMT 2016-12-28 00:00:00 UCT +0000 Etc/UCT 2016-12-28 00:00:00 UTC +0000 Etc/UTC 2016-12-28 00:00:00 GMT +0000 Europe/Dublin 2016-12-28 00:00:00 WET +0000 Europe/Lisbon 2016-12-28 00:00:00 GMT +0000 Europe/London 2016-12-28 00:00:00 WET +0000 WET These are all the timezones it is midnight at 2016-12-28 01:00:00 UTC 2016-12-28 00:00:00 EGT -0100 America/Scoresbysund 2016-12-28 00:00:00 AZOT -0100 Atlantic/Azores 2016-12-28 00:00:00 CVT -0100 Atlantic/Cape_Verde 2016-12-28 00:00:00 -01 -0100 Etc/GMT+1 These are all the timezones it is midnight at 2016-12-28 02:00:00 UTC 2016-12-28 00:00:00 FNT -0200 America/Noronha 2016-12-28 00:00:00 BRST -0200 America/Sao_Paulo 2016-12-28 00:00:00 GST -0200 Atlantic/South_Georgia 2016-12-28 00:00:00 -02 -0200 Etc/GMT+2 These are all the timezones it is midnight at 2016-12-28 03:00:00 UTC 2016-12-28 00:00:00 BRT -0300 America/Araguaina 2016-12-28 00:00:00 ART -0300 America/Argentina/Buenos_Aires 2016-12-28 00:00:00 ART -0300 America/Argentina/Catamarca 2016-12-28 00:00:00 ART -0300 America/Argentina/Cordoba 2016-12-28 00:00:00 ART -0300 America/Argentina/Jujuy 2016-12-28 00:00:00 ART -0300 America/Argentina/La_Rioja 2016-12-28 00:00:00 ART -0300 America/Argentina/Mendoza 2016-12-28 00:00:00 ART -0300 America/Argentina/Rio_Gallegos 2016-12-28 00:00:00 ART -0300 America/Argentina/Salta 2016-12-28 00:00:00 ART -0300 America/Argentina/San_Juan 2016-12-28 00:00:00 ART -0300 America/Argentina/San_Luis 2016-12-28 00:00:00 ART -0300 America/Argentina/Tucuman 2016-12-28 00:00:00 ART -0300 America/Argentina/Ushuaia 2016-12-28 00:00:00 PYST -0300 America/Asuncion 2016-12-28 00:00:00 BRT -0300 America/Bahia 2016-12-28 00:00:00 BRT -0300 America/Belem 2016-12-28 00:00:00 AMST -0300 America/Campo_Grande 2016-12-28 00:00:00 GFT -0300 America/Cayenne 2016-12-28 00:00:00 AMST -0300 America/Cuiaba 2016-12-28 00:00:00 BRT -0300 America/Fortaleza 2016-12-28 00:00:00 WGT -0300 America/Godthab 2016-12-28 00:00:00 BRT -0300 America/Maceio 2016-12-28 00:00:00 PMST -0300 America/Miquelon 2016-12-28 00:00:00 UYT -0300 America/Montevideo 2016-12-28 00:00:00 SRT -0300 America/Paramaribo 2016-12-28 00:00:00 BRT -0300 America/Recife 2016-12-28 00:00:00 BRT -0300 America/Santarem 2016-12-28 00:00:00 CLST -0300 America/Santiago 2016-12-28 00:00:00 CLST -0300 Antarctica/Palmer 2016-12-28 00:00:00 -03 -0300 Antarctica/Rothera 2016-12-28 00:00:00 FKST -0300 Atlantic/Stanley 2016-12-28 00:00:00 -03 -0300 Etc/GMT+3 These are all the timezones it is midnight at 2016-12-28 04:00:00 UTC 2016-12-28 00:00:00 AST -0400 America/Barbados 2016-12-28 00:00:00 AST -0400 America/Blanc-Sablon 2016-12-28 00:00:00 AMT -0400 America/Boa_Vista 2016-12-28 00:00:00 VET -0400 America/Caracas 2016-12-28 00:00:00 AST -0400 America/Curacao 2016-12-28 00:00:00 AST -0400 America/Glace_Bay 2016-12-28 00:00:00 AST -0400 America/Goose_Bay 2016-12-28 00:00:00 AST -0400 America/Grand_Turk 2016-12-28 00:00:00 GYT -0400 America/Guyana 2016-12-28 00:00:00 AST -0400 America/Halifax 2016-12-28 00:00:00 BOT -0400 America/La_Paz 2016-12-28 00:00:00 AMT -0400 America/Manaus 2016-12-28 00:00:00 AST -0400 America/Martinique 2016-12-28 00:00:00 AST -0400 America/Moncton 2016-12-28 00:00:00 AST -0400 America/Port_of_Spain 2016-12-28 00:00:00 AMT -0400 America/Porto_Velho 2016-12-28 00:00:00 AST -0400 America/Puerto_Rico 2016-12-28 00:00:00 AST -0400 America/Santo_Domingo 2016-12-28 00:00:00 AST -0400 America/Thule 2016-12-28 00:00:00 AST -0400 Atlantic/Bermuda 2016-12-28 00:00:00 -04 -0400 Etc/GMT+4 These are all the timezones it is midnight at 2016-12-28 05:00:00 UTC 2016-12-28 00:00:00 EST -0500 America/Atikokan 2016-12-28 00:00:00 COT -0500 America/Bogota 2016-12-28 00:00:00 EST -0500 America/Cancun 2016-12-28 00:00:00 EST -0500 America/Detroit 2016-12-28 00:00:00 ACT -0500 America/Eirunepe 2016-12-28 00:00:00 ECT -0500 America/Guayaquil 2016-12-28 00:00:00 CST -0500 America/Havana 2016-12-28 00:00:00 EST -0500 America/Indiana/Indianapolis 2016-12-28 00:00:00 EST -0500 America/Indiana/Marengo 2016-12-28 00:00:00 EST -0500 America/Indiana/Petersburg 2016-12-28 00:00:00 EST -0500 America/Indiana/Vevay 2016-12-28 00:00:00 EST -0500 America/Indiana/Vincennes 2016-12-28 00:00:00 EST -0500 America/Indiana/Winamac 2016-12-28 00:00:00 EST -0500 America/Iqaluit 2016-12-28 00:00:00 EST -0500 America/Jamaica 2016-12-28 00:00:00 EST -0500 America/Kentucky/Louisville 2016-12-28 00:00:00 EST -0500 America/Kentucky/Monticello 2016-12-28 00:00:00 PET -0500 America/Lima 2016-12-28 00:00:00 EST -0500 America/Nassau 2016-12-28 00:00:00 EST -0500 America/New_York 2016-12-28 00:00:00 EST -0500 America/Nipigon 2016-12-28 00:00:00 EST -0500 America/Panama 2016-12-28 00:00:00 EST -0500 America/Pangnirtung 2016-12-28 00:00:00 EST -0500 America/Port-au-Prince 2016-12-28 00:00:00 ACT -0500 America/Rio_Branco 2016-12-28 00:00:00 EST -0500 America/Thunder_Bay 2016-12-28 00:00:00 EST -0500 America/Toronto 2016-12-28 00:00:00 EST -0500 EST 2016-12-28 00:00:00 EST -0500 EST5EDT 2016-12-28 00:00:00 -05 -0500 Etc/GMT+5 2016-12-28 00:00:00 EASST -0500 Pacific/Easter These are all the timezones it is midnight at 2016-12-28 06:00:00 UTC 2016-12-28 00:00:00 CST -0600 America/Bahia_Banderas 2016-12-28 00:00:00 CST -0600 America/Belize 2016-12-28 00:00:00 CST -0600 America/Chicago 2016-12-28 00:00:00 CST -0600 America/Costa_Rica 2016-12-28 00:00:00 CST -0600 America/El_Salvador 2016-12-28 00:00:00 CST -0600 America/Guatemala 2016-12-28 00:00:00 CST -0600 America/Indiana/Knox 2016-12-28 00:00:00 CST -0600 America/Indiana/Tell_City 2016-12-28 00:00:00 CST -0600 America/Managua 2016-12-28 00:00:00 CST -0600 America/Matamoros 2016-12-28 00:00:00 CST -0600 America/Menominee 2016-12-28 00:00:00 CST -0600 America/Merida 2016-12-28 00:00:00 CST -0600 America/Mexico_City 2016-12-28 00:00:00 CST -0600 America/Monterrey 2016-12-28 00:00:00 CST -0600 America/North_Dakota/Beulah 2016-12-28 00:00:00 CST -0600 America/North_Dakota/Center 2016-12-28 00:00:00 CST -0600 America/North_Dakota/New_Salem 2016-12-28 00:00:00 CST -0600 America/Rainy_River 2016-12-28 00:00:00 CST -0600 America/Rankin_Inlet 2016-12-28 00:00:00 CST -0600 America/Regina 2016-12-28 00:00:00 CST -0600 America/Resolute 2016-12-28 00:00:00 CST -0600 America/Swift_Current 2016-12-28 00:00:00 CST -0600 America/Tegucigalpa 2016-12-28 00:00:00 CST -0600 America/Winnipeg 2016-12-28 00:00:00 CST -0600 CST6CDT 2016-12-28 00:00:00 -06 -0600 Etc/GMT+6 2016-12-28 00:00:00 GALT -0600 Pacific/Galapagos These are all the timezones it is midnight at 2016-12-28 07:00:00 UTC 2016-12-28 00:00:00 MST -0700 America/Boise 2016-12-28 00:00:00 MST -0700 America/Cambridge_Bay 2016-12-28 00:00:00 MST -0700 America/Chihuahua 2016-12-28 00:00:00 MST -0700 America/Creston 2016-12-28 00:00:00 MST -0700 America/Dawson_Creek 2016-12-28 00:00:00 MST -0700 America/Denver 2016-12-28 00:00:00 MST -0700 America/Edmonton 2016-12-28 00:00:00 MST -0700 America/Fort_Nelson 2016-12-28 00:00:00 MST -0700 America/Hermosillo 2016-12-28 00:00:00 MST -0700 America/Inuvik 2016-12-28 00:00:00 MST -0700 America/Mazatlan 2016-12-28 00:00:00 MST -0700 America/Ojinaga 2016-12-28 00:00:00 MST -0700 America/Phoenix 2016-12-28 00:00:00 MST -0700 America/Yellowknife 2016-12-28 00:00:00 -07 -0700 Etc/GMT+7 2016-12-28 00:00:00 MST -0700 MST 2016-12-28 00:00:00 MST -0700 MST7MDT These are all the timezones it is midnight at 2016-12-28 08:00:00 UTC 2016-12-28 00:00:00 PST -0800 America/Dawson 2016-12-28 00:00:00 PST -0800 America/Los_Angeles 2016-12-28 00:00:00 PST -0800 America/Tijuana 2016-12-28 00:00:00 PST -0800 America/Vancouver 2016-12-28 00:00:00 PST -0800 America/Whitehorse 2016-12-28 00:00:00 -08 -0800 Etc/GMT+8 2016-12-28 00:00:00 PST -0800 PST8PDT 2016-12-28 00:00:00 PST -0800 Pacific/Pitcairn These are all the timezones it is midnight at 2016-12-28 09:00:00 UTC 2016-12-28 00:00:00 AKST -0900 America/Anchorage 2016-12-28 00:00:00 AKST -0900 America/Juneau 2016-12-28 00:00:00 AKST -0900 America/Metlakatla 2016-12-28 00:00:00 AKST -0900 America/Nome 2016-12-28 00:00:00 AKST -0900 America/Sitka 2016-12-28 00:00:00 AKST -0900 America/Yakutat 2016-12-28 00:00:00 -09 -0900 Etc/GMT+9 2016-12-28 00:00:00 GAMT -0900 Pacific/Gambier These are all the timezones it is midnight at 2016-12-28 10:00:00 UTC 2016-12-28 00:00:00 HST -1000 America/Adak 2016-12-28 00:00:00 -10 -1000 Etc/GMT+10 2016-12-28 00:00:00 HST -1000 HST 2016-12-28 00:00:00 HST -1000 Pacific/Honolulu 2016-12-28 00:00:00 CKT -1000 Pacific/Rarotonga 2016-12-28 00:00:00 TAHT -1000 Pacific/Tahiti 2016-12-29 00:00:00 +14 +1400 Etc/GMT-14 2016-12-29 00:00:00 WSDT +1400 Pacific/Apia 2016-12-29 00:00:00 LINT +1400 Pacific/Kiritimati 2016-12-29 00:00:00 +14 +1400 Pacific/Tongatapu These are all the timezones it is midnight at 2016-12-28 11:00:00 UTC 2016-12-28 00:00:00 -11 -1100 Etc/GMT+11 2016-12-28 00:00:00 NUT -1100 Pacific/Niue 2016-12-28 00:00:00 SST -1100 Pacific/Pago_Pago 2016-12-29 00:00:00 +13 +1300 Etc/GMT-13 2016-12-29 00:00:00 NZDT +1300 Pacific/Auckland 2016-12-29 00:00:00 PHOT +1300 Pacific/Enderbury 2016-12-29 00:00:00 TKT +1300 Pacific/Fakaofo 2016-12-29 00:00:00 FJST +1300 Pacific/Fiji These are all the timezones it is midnight at 2016-12-28 12:00:00 UTC 2016-12-28 00:00:00 -12 -1200 Etc/GMT+12 2016-12-29 00:00:00 +12 +1200 Asia/Anadyr 2016-12-29 00:00:00 +12 +1200 Asia/Kamchatka 2016-12-29 00:00:00 +12 +1200 Etc/GMT-12 2016-12-29 00:00:00 TVT +1200 Pacific/Funafuti 2016-12-29 00:00:00 MHT +1200 Pacific/Kwajalein 2016-12-29 00:00:00 MHT +1200 Pacific/Majuro 2016-12-29 00:00:00 NRT +1200 Pacific/Nauru 2016-12-29 00:00:00 GILT +1200 Pacific/Tarawa 2016-12-29 00:00:00 WAKT +1200 Pacific/Wake 2016-12-29 00:00:00 WFT +1200 Pacific/Wallis These are all the timezones it is midnight at 2016-12-28 13:00:00 UTC 2016-12-29 00:00:00 +11 +1100 Antarctica/Casey 2016-12-29 00:00:00 MIST +1100 Antarctica/Macquarie 2016-12-29 00:00:00 +11 +1100 Asia/Magadan 2016-12-29 00:00:00 +11 +1100 Asia/Sakhalin 2016-12-29 00:00:00 +11 +1100 Asia/Srednekolymsk 2016-12-29 00:00:00 AEDT +1100 Australia/Currie 2016-12-29 00:00:00 AEDT +1100 Australia/Hobart 2016-12-29 00:00:00 LHDT +1100 Australia/Lord_Howe 2016-12-29 00:00:00 AEDT +1100 Australia/Melbourne 2016-12-29 00:00:00 AEDT +1100 Australia/Sydney 2016-12-29 00:00:00 +11 +1100 Etc/GMT-11 2016-12-29 00:00:00 BST +1100 Pacific/Bougainville 2016-12-29 00:00:00 VUT +1100 Pacific/Efate 2016-12-29 00:00:00 SBT +1100 Pacific/Guadalcanal 2016-12-29 00:00:00 KOST +1100 Pacific/Kosrae 2016-12-29 00:00:00 NFT +1100 Pacific/Norfolk 2016-12-29 00:00:00 NCT +1100 Pacific/Noumea 2016-12-29 00:00:00 PONT +1100 Pacific/Pohnpei |
笔记:
-
2016-12-28 10:00:00 UTC列出了Pacific / Honolulu和Pacific / Tongatapu的结果(以及其他几个)。
-
这些结果列出了所有的
-10/+14 和-11/+13 配对,以及其他一些配对,但是其他几个配对仅涉及"海上"时区,例如"Etc / GMT + 12"。 -
如果您改变要探索的节目2016-10-16
America/Sao_Paulo 从未列出,虽然它列于2016-12-28,因为America/Sao_Paulo 在2016-10-16没有午夜。但是你确实在2016-10-16 03:00:00 UTC(偏移-0300)下列出了America/Bahia 。 -
更改程序以探索2016-11-06显示
America/Havana 在2016-11-06 04:00:00 UTC和2016-11-06 05:00:00 UTC下列出。 -
在这里没有突出显示的例子中,有一个独特的时区,它对于给定的UTC时间点是午夜。可能存在这样的时区,其时区的UTC偏移不是整数小时。
啊,是的,这里有几个:
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 | These are all the timezones it is midnight at 2016-12-27 09:30:00 UTC 2016-12-27 00:00:00 MART -0930 Pacific/Marquesas These are all the timezones it is midnight at 2016-12-27 10:15:00 UTC 2016-12-28 00:00:00 CHADT +1345 Pacific/Chatham These are all the timezones it is midnight at 2016-12-27 14:30:00 UTC 2016-12-28 00:00:00 ACST +0930 Australia/Darwin These are all the timezones it is midnight at 2016-12-27 15:15:00 UTC 2016-12-28 00:00:00 ACWST +0845 Australia/Eucla These are all the timezones it is midnight at 2016-12-27 15:30:00 UTC 2016-12-28 00:00:00 KST +0830 Asia/Pyongyang These are all the timezones it is midnight at 2016-12-27 18:15:00 UTC 2016-12-28 00:00:00 NPT +0545 Asia/Kathmandu These are all the timezones it is midnight at 2016-12-27 19:30:00 UTC 2016-12-28 00:00:00 AFT +0430 Asia/Kabul These are all the timezones it is midnight at 2016-12-27 20:30:00 UTC 2016-12-28 00:00:00 IRST +0330 Asia/Tehran These are all the timezones it is midnight at 2016-12-28 03:30:00 UTC 2016-12-28 00:00:00 NST -0330 America/St_Johns |
Matt Johnson的回答是正确的。
- 如果您确定存储在数据库中的那一刻代表某个时区的某一时刻的第一时刻,您可以获得一个日期。
- 您可以猜测时区,但是当多个区域在此时共享与UTC的偏移时,您无法确定原始时区。
java.time
下面是一些使用现代java.time类的Java代码。
Imagine you take a local date, say 2016-12-28, in a given time zone, say America/New_York, and convert the start of that date into UTC (in this case 2016-12-28T05:00:00Z).
请注意,我们让java.time通过
1 2 3 | LocalDate localDate = LocalDate.parse("2016-12-28" ) ; ZoneId zNewYork = ZoneId.of("America/New_York" ) ; ZonedDateTime zdtNewYork = localDate.atStartOfDay( zNewYork ) ; // First moment of the day in that zone on that date. |
通过提取
1 | Instant instant = zdtNewYork.toInstant() ; |
以类似于SQL-standard
1 | myPreparedStatement.setObject( … , instant ) ; |
get back to the original local date without knowing the time zone?
检索。
1 | Instant instant = myResultSet.getObject( … , Instant.class ) ; |
现在试验每个时区。仅供参考,请参阅维基百科的区域名称列表,但该页面可能已过时。
对于每个区域,将我们的
对于每个
从第二个
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | List< ZoneId > hits = new ArrayList<>() ; LocalDate originalLocalDate = null ; Set< String > zoneIds = ZoneId.getAvailableZoneIds() ; // Gets the set of available zone IDs. for( String zoneId : zoneIds ) { ZoneId z = ZoneId.of( zoneId ) ; // Get zone with that name. ZonedDateTime zdt = instant.atZone( z ) ; LocalDate ld = zdt.toLocalDate() ; // Extract the date-only value, dropping the time-of-day and dropping the time zone. ZonedDateTime startOfDay = ld.atStartOfDay( z ) ; // Determine first moment of the day on that date in that zone. Instant instantOfStartOfDay = startOfDay.toInstant() ; // Adjust back to UTC. boolean hit = instant.equals( instantOfStartOfDay ) ; if( hit ) { originalLocalDate = ld ; hits.add( z ) ; // Collect this time zone as the zone possibly used originally. } } |
请参阅IdeOne.com上的此代码。
运行时,我们看到该日期的
originalLocalDate.toString(): 2016-12-28
hits.toString(): [America/Panama, America/Indiana/Petersburg, America/Eirunepe, Cuba, Etc/GMT+5, Pacific/Easter, America/Fort_Wayne, America/Havana, America/Porto_Acre, US/Michigan, America/Louisville, America/Guayaquil, America/Indiana/Vevay, America/Indiana/Vincennes, America/Indianapolis, America/Iqaluit, America/Kentucky/Louisville, EST5EDT, America/Nassau, America/Jamaica, America/Atikokan, America/Kentucky/Monticello, America/Coral_Harbour, America/Cayman, Chile/EasterIsland, America/Indiana/Indianapolis, America/Thunder_Bay, America/Indiana/Marengo, America/Bogota, SystemV/EST5, US/Eastern, Canada/Eastern, America/Port-au-Prince, America/Nipigon, Brazil/Acre, US/East-Indiana, America/Cancun, America/Lima, America/Rio_Branco, America/Detroit, Jamaica, America/Pangnirtung, America/Montreal, America/Indiana/Winamac, America/New_York, America/Toronto, SystemV/EST5EDT]
请注意,生成的区域列表可能不明显。某些区域名称是别名,其中一个区域具有多个名称。例如,旧的
关于java.time
java.time框架内置于Java 8及更高版本中。这些类取代了麻烦的旧遗留日期时间类,例如
现在处于维护模式的Joda-Time项目建议迁移到java.time类。
要了解更多信息,请参阅Oracle教程。并搜索Stack Overflow以获取许多示例和解释。规范是JSR 310。
您可以直接与数据库交换java.time对象。使用符合JDBC 4.2或更高版本的JDBC驱动程序。不需要字符串,不需要
从哪里获取java.time类?
-
Java SE 8,Java SE 9,Java SE 10及更高版本
- 内置。
- 带有捆绑实现的标准Java API的一部分。
- Java 9增加了一些小功能和修复。
-
Java SE 6和Java SE 7
- 许多java.time功能都被反向移植到Java 6&amp; 7在ThreeTen-Backport。
-
Android的
- 更高版本的Android捆绑java.time类的实现。
- 对于早期的Android(<26),ThreeTenABP项目采用ThreeTen-Backport(如上所述)。请参见如何使用ThreeTenABP ....
ThreeTen-Extra项目使用其他类扩展了java.time。该项目是未来可能添加到java.time的试验场。您可以在这里找到一些有用的类,例如