java.time

Question

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（在这种情况下2016-12-28T05：00：00Z ）。

是否可以从UTC时间返回到原始本地日期而不知道时区？你所知道的是UTC时间代表某些当地午夜/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。）

Answer 1

使用此free, open-source C++ library，我可以计算此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。

以下是代码：

#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\n", 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() << '\n';
        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() << '\n';
        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() << '\n';
        std::cout << '\n';
    }
}

代码创建一个UTC时间戳和偏移对，并将其提供给find_by_offset，它遍历所有时区，并在每个时区查询该时间戳的偏移量。如果时区的偏移量与所需的偏移量匹配，则会在结果中添加zoned_time（zoned_time是时区与时间戳的配对。）

以下是2016-12-28日期可能有午夜的所有结果：

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

注意：

2016-12-28 10:00:00 UTC在其结果中列出太平洋/檀香山和太平洋/汤加塔普（以及其他几个）。
这些结果列出了-10/+14和-11/+13配对的所有以及其他几个，但其他几个只涉及“海上”时区如“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没有午夜-16。但您确实在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列于2016-11-06 04:00:00 UTC和2016-11-06 05:00:00 UTC
在此处突出显示的示例的 none 中，有一个唯一时区，在此时间点为给定UTC时间点的午夜。可能存在这样一个时区的时区，其UTC时间偏差不是整数小时。

啊，是的，这里有几个：

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

Answer 2

在某些限制条件下，可以识别时区偏移量（UTC-05:00），但不能识别原始时区（America/New_York）。霍华德在答案中表示，你只能列出当时偏移可能属于的可能时区。还有其他边缘情况使这个问题变得困难：

您明确说明了如何无法确定国际日期变更线附近的抵消日期。
- 例如，考虑2016-12-31T10:00:00Z。这可能是2016-12-31T00:00:00-10:00（可能是Pacific/Honolulu），也可能是2017-01-01T00:00:00+14:00（可能是Pacific/Tongatapu）。
- -10/+14和-11/+13配对都是可能的，但地球上没有人居住的地方实际使用-12。因此，如果你的价值正好在中午，那么它们可能是+12，除非你在海上与船只打交道。
您所期望的时区中的本地午夜值可能不存在。
- 例如，2016-10-16T03:00:00Z是America/Sao_Paulo和America/Bahia（都在巴西）的当天开始。但是，America/Sao_Paulo的当地时间为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。
您所期望的时区中的本地午夜值可能会存在两次。
- 例如，在America/Havana中，2016-11-06T04:00:00Z和2016-11-06T05:00:00Z的本地时间为00:00，原因是他们的DST回退过渡。

因此，在一般情况下，您可以将大多数解析回原始偏移量，但对于-10，{{1}的时区，您会有歧义}}，-11或+13偏移，以及在午夜（春季）或凌晨1:00（秋季）进行DST过渡的时区。（请记住，北半球/南半球的春/秋季不同。）

Answer 3

Answer by Matt Johnson是正确的。

如果您确定数据库中存储的时刻代表某天的第一时刻，则可以获取日期。
您可以猜测有关时区，但是当多个时区共享从UTC偏移时，您不能确定原始时区。

java.time

这是一些使用现代 java.time 类的Java代码。

假设您在给定的时区（例如America / New_York）中输入本地日期（例如2016-12-28），然后将该日期的开始时间转换为UTC（在这种情况下为2016-12-28T05：00：00Z ）。

请注意，我们通过LocalDate::atStartOfDay方法让 java.time 确定一天中的第一时刻。不要以为一天从00:00:00开始。诸如夏令时之类的异常表示一天可能在另一个时间（如01:00:00）开始。

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Instant调整为UTC值。根据定义，Instant始终采用UTC。

Instant instant = zdtNewYork.toInstant() ;

在数据库中存储的列类型类似于SQL标准TIMESTAMP WITH TIME ZONE。

myPreparedStatement.setObject( … , instant ) ;

在不知道时区的情况下返回原始的本地日期？

检索。

Instant instant = myResultSet.getObject( … , Instant.class ) ;

现在尝试每个时区。仅供参考，请参阅list of zone names at Wikipedia，尽管该页面可能已过时。

对于每个区域，将我们的Instant（我们的UTC时刻）调整到该区域，以获取ZonedDateTime对象。某个时刻，时间轴上的同一点，但挂钟时间不同。

对于每个ZonedDateTime，仅提取日期，不提取日期和时区。渲染LocalDate对象。要求LocalDate确定正在考虑的我们时区中的一天的第一时刻（可能在00:00:00发生或可能不发生）。这将产生另一个ZonedDateTime对象。

从第二个ZonedDateTime中提取一个Instant，以调整回UTC。将这个新的Instant对象与原始Instant进行比较。如果它们相同，那么我们很受欢迎。我们已经确定了存储在数据库中的一天开始的时区。因此，我们上面产生的LocalDate与原始存储在我们数据库中的日期相同。

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.
    }
}

请参阅此code run live at IdeOne.com。

运行时，我们看到该日期的America/New_York时区比UTC偏移了五个小时。您可以从此列表中看到许多其他时区共享相同的-05:00偏移量。

originalLocalDate.toString（）：2016-12-28

hits.toString（）：[美国/巴拿马，美国/印第安纳州/彼得斯堡，美国/埃鲁尼佩，古巴，Etc / GMT + 5，太平洋/复活节，美国/ Fort_Wayne，美国/哈瓦那，美国/ Porto_Acre，美国/密歇根州，美国/路易斯维尔，美国/瓜亚基尔，美国/印第安纳州/韦韦，美国/印第安纳州/文森斯，美国/印第安纳波利斯，美国/伊卡卢伊特，美国/肯塔基州/路易斯维尔，EST5EDT，美国/拿骚，美国/牙买加，美国/ Atikokan，美洲/肯塔基州/蒙蒂塞洛，美洲/珊瑚港，美洲/开曼，智利/东岛，美洲/印第安纳州/印第安纳波利斯，美洲/雷霆湾，美洲/印第安纳州/马伦戈，美洲/波哥大，SystemV / EST5，美洲/东部，加拿大/东部，美国/太子港，美国/尼皮贡，巴西/英亩，美国/东印第安纳州，美国/坎昆，美国/利马，美国/里奥布兰科，美国/底特律，牙买加，美国/庞尼通，美国/蒙特利尔，美国/印第安纳州/威纳马克，美国/纽约，美国/多伦多，SystemV / EST5EDT]

请注意，区域的结果列表可能不会不同。一些区域名称是别名，其中一个区域具有多个名称。例如，旧的Asia/Calcutta现在是Asia/Kolkata。

关于 java.time

java.time框架已内置在Java 8及更高版本中。这些类取代了麻烦的旧legacy日期时间类，例如java.util.Date，Calendar和SimpleDateFormat。

目前位于Joda-Time的maintenance mode项目建议迁移到java.time类。

要了解更多信息，请参见Oracle Tutorial。并在Stack Overflow中搜索许多示例和说明。规格为JSR 310。

您可以直接与数据库交换 java.time 对象。使用符合JDBC driver或更高版本的JDBC 4.2。不需要字符串，不需要java.sql.*类。

在哪里获取java.time类？

Java SE 8，Java SE 9，Java SE 10和更高版本
- 内置。
- 带有捆绑实施的标准Java API的一部分。
- Java 9添加了一些次要功能和修复。
Java SE 6和Java SE 7
- 许多Java.time功能都已在ThreeTen-Backport中反向移植到Java 6和7。
Android
- java.time 类的Android捆绑包实现的最新版本。
- 对于较早的Android（<26），ThreeTenABP项目改编为ThreeTen-Backport（如上所述）。参见How to use ThreeTenABP…。

ThreeTen-Extra项目使用其他类扩展了java.time。该项目为将来可能在java.time中添加内容提供了一个试验场。您可能会在这里找到一些有用的类，例如Interval，YearWeek，YearQuarter和more。

是否可以从表示当地午夜的UTC时间计算本地日期？

3 个答案:

java.time

关于 java.time