library(tidyverse)
library(lubridate)タイムゾーンという言葉を聞いたことはありますでしょうか？
日本で夜の9時の時、アメリカでは朝のXX時というあれです。
実は、Rは、日本時間と現地時間を換算するツールとしても利用できます。
やってみましょう。
akasi <- as_datetime("2000-1-1 9:00:00",tz="Japan")
akasi[1] "2000-01-01 09:00:00 JST"日本の明石で2000年1月1日の朝9時だった場合は、tzをJapanと指定してあげてその時刻を作成することができます。(そうすると、JSTという略がついていますね？)
では、この時刻、アメリカのハワイ州ホノルルにある時計の時間(現地時間)であればどうなるでしょうか?
Rなら簡単です
lubridate::with_tz(akasi, "Pacific/Honolulu")[1] "1999-12-31 14:00:00 HST"はい。1999年12月31日 14:00 HSTという結果でした。
これがあれば、その土地のタイムゾーンを表すテキストさえわかれば、自由自在に時刻を換算することができます。
もちろん、これを覚えるのは大変なので、
OlsonNames() [1] "Africa/Abidjan" "Africa/Accra"
[3] "Africa/Addis_Ababa" "Africa/Algiers"
[5] "Africa/Asmara" "Africa/Asmera"
[7] "Africa/Bamako" "Africa/Bangui"
[9] "Africa/Banjul" "Africa/Bissau"
[11] "Africa/Blantyre" "Africa/Brazzaville"
[13] "Africa/Bujumbura" "Africa/Cairo"
[15] "Africa/Casablanca" "Africa/Ceuta"
[17] "Africa/Conakry" "Africa/Dakar"
[19] "Africa/Dar_es_Salaam" "Africa/Djibouti"
[21] "Africa/Douala" "Africa/El_Aaiun"
[23] "Africa/Freetown" "Africa/Gaborone"
[25] "Africa/Harare" "Africa/Johannesburg"
[27] "Africa/Juba" "Africa/Kampala"
[29] "Africa/Khartoum" "Africa/Kigali"
[31] "Africa/Kinshasa" "Africa/Lagos"
[33] "Africa/Libreville" "Africa/Lome"
[35] "Africa/Luanda" "Africa/Lubumbashi"
[37] "Africa/Lusaka" "Africa/Malabo"
[39] "Africa/Maputo" "Africa/Maseru"
[41] "Africa/Mbabane" "Africa/Mogadishu"
[43] "Africa/Monrovia" "Africa/Nairobi"
[45] "Africa/Ndjamena" "Africa/Niamey"
[47] "Africa/Nouakchott" "Africa/Ouagadougou"
[49] "Africa/Porto-Novo" "Africa/Sao_Tome"
[51] "Africa/Timbuktu" "Africa/Tripoli"
[53] "Africa/Tunis" "Africa/Windhoek"
[55] "America/Adak" "America/Anchorage"
[57] "America/Anguilla" "America/Antigua"
[59] "America/Araguaina" "America/Argentina/Buenos_Aires"
[61] "America/Argentina/Catamarca" "America/Argentina/ComodRivadavia"
[63] "America/Argentina/Cordoba" "America/Argentina/Jujuy"
[65] "America/Argentina/La_Rioja" "America/Argentina/Mendoza"
[67] "America/Argentina/Rio_Gallegos" "America/Argentina/Salta"
[69] "America/Argentina/San_Juan" "America/Argentina/San_Luis"
[71] "America/Argentina/Tucuman" "America/Argentina/Ushuaia"
[73] "America/Aruba" "America/Asuncion"
[75] "America/Atikokan" "America/Atka"
[77] "America/Bahia" "America/Bahia_Banderas"
[79] "America/Barbados" "America/Belem"
[81] "America/Belize" "America/Blanc-Sablon"
[83] "America/Boa_Vista" "America/Bogota"
[85] "America/Boise" "America/Buenos_Aires"
[87] "America/Cambridge_Bay" "America/Campo_Grande"
[89] "America/Cancun" "America/Caracas"
[91] "America/Catamarca" "America/Cayenne"
[93] "America/Cayman" "America/Chicago"
[95] "America/Chihuahua" "America/Ciudad_Juarez"
[97] "America/Coral_Harbour" "America/Cordoba"
[99] "America/Costa_Rica" "America/Creston"
[101] "America/Cuiaba" "America/Curacao"
[103] "America/Danmarkshavn" "America/Dawson"
[105] "America/Dawson_Creek" "America/Denver"
[107] "America/Detroit" "America/Dominica"
[109] "America/Edmonton" "America/Eirunepe"
[111] "America/El_Salvador" "America/Ensenada"
[113] "America/Fort_Nelson" "America/Fort_Wayne"
[115] "America/Fortaleza" "America/Glace_Bay"
[117] "America/Godthab" "America/Goose_Bay"
[119] "America/Grand_Turk" "America/Grenada"
[121] "America/Guadeloupe" "America/Guatemala"
[123] "America/Guayaquil" "America/Guyana"
[125] "America/Halifax" "America/Havana"
[127] "America/Hermosillo" "America/Indiana/Indianapolis"
[129] "America/Indiana/Knox" "America/Indiana/Marengo"
[131] "America/Indiana/Petersburg" "America/Indiana/Tell_City"
[133] "America/Indiana/Vevay" "America/Indiana/Vincennes"
[135] "America/Indiana/Winamac" "America/Indianapolis"
[137] "America/Inuvik" "America/Iqaluit"
[139] "America/Jamaica" "America/Jujuy"
[141] "America/Juneau" "America/Kentucky/Louisville"
[143] "America/Kentucky/Monticello" "America/Knox_IN"
[145] "America/Kralendijk" "America/La_Paz"
[147] "America/Lima" "America/Los_Angeles"
[149] "America/Louisville" "America/Lower_Princes"
[151] "America/Maceio" "America/Managua"
[153] "America/Manaus" "America/Marigot"
[155] "America/Martinique" "America/Matamoros"
[157] "America/Mazatlan" "America/Mendoza"
[159] "America/Menominee" "America/Merida"
[161] "America/Metlakatla" "America/Mexico_City"
[163] "America/Miquelon" "America/Moncton"
[165] "America/Monterrey" "America/Montevideo"
[167] "America/Montreal" "America/Montserrat"
[169] "America/Nassau" "America/New_York"
[171] "America/Nipigon" "America/Nome"
[173] "America/Noronha" "America/North_Dakota/Beulah"
[175] "America/North_Dakota/Center" "America/North_Dakota/New_Salem"
[177] "America/Nuuk" "America/Ojinaga"
[179] "America/Panama" "America/Pangnirtung"
[181] "America/Paramaribo" "America/Phoenix"
[183] "America/Port-au-Prince" "America/Port_of_Spain"
[185] "America/Porto_Acre" "America/Porto_Velho"
[187] "America/Puerto_Rico" "America/Punta_Arenas"
[189] "America/Rainy_River" "America/Rankin_Inlet"
[191] "America/Recife" "America/Regina"
[193] "America/Resolute" "America/Rio_Branco"
[195] "America/Rosario" "America/Santa_Isabel"
[197] "America/Santarem" "America/Santiago"
[199] "America/Santo_Domingo" "America/Sao_Paulo"
[201] "America/Scoresbysund" "America/Shiprock"
[203] "America/Sitka" "America/St_Barthelemy"
[205] "America/St_Johns" "America/St_Kitts"
[207] "America/St_Lucia" "America/St_Thomas"
[209] "America/St_Vincent" "America/Swift_Current"
[211] "America/Tegucigalpa" "America/Thule"
[213] "America/Thunder_Bay" "America/Tijuana"
[215] "America/Toronto" "America/Tortola"
[217] "America/Vancouver" "America/Virgin"
[219] "America/Whitehorse" "America/Winnipeg"
[221] "America/Yakutat" "America/Yellowknife"
[223] "Antarctica/Casey" "Antarctica/Davis"
[225] "Antarctica/DumontDUrville" "Antarctica/Macquarie"
[227] "Antarctica/Mawson" "Antarctica/McMurdo"
[229] "Antarctica/Palmer" "Antarctica/Rothera"
[231] "Antarctica/South_Pole" "Antarctica/Syowa"
[233] "Antarctica/Troll" "Antarctica/Vostok"
[235] "Arctic/Longyearbyen" "Asia/Aden"
[237] "Asia/Almaty" "Asia/Amman"
[239] "Asia/Anadyr" "Asia/Aqtau"
[241] "Asia/Aqtobe" "Asia/Ashgabat"
[243] "Asia/Ashkhabad" "Asia/Atyrau"
[245] "Asia/Baghdad" "Asia/Bahrain"
[247] "Asia/Baku" "Asia/Bangkok"
[249] "Asia/Barnaul" "Asia/Beirut"
[251] "Asia/Bishkek" "Asia/Brunei"
[253] "Asia/Calcutta" "Asia/Chita"
[255] "Asia/Choibalsan" "Asia/Chongqing"
[257] "Asia/Chungking" "Asia/Colombo"
[259] "Asia/Dacca" "Asia/Damascus"
[261] "Asia/Dhaka" "Asia/Dili"
[263] "Asia/Dubai" "Asia/Dushanbe"
[265] "Asia/Famagusta" "Asia/Gaza"
[267] "Asia/Harbin" "Asia/Hebron"
[269] "Asia/Ho_Chi_Minh" "Asia/Hong_Kong"
[271] "Asia/Hovd" "Asia/Irkutsk"
[273] "Asia/Istanbul" "Asia/Jakarta"
[275] "Asia/Jayapura" "Asia/Jerusalem"
[277] "Asia/Kabul" "Asia/Kamchatka"
[279] "Asia/Karachi" "Asia/Kashgar"
[281] "Asia/Kathmandu" "Asia/Katmandu"
[283] "Asia/Khandyga" "Asia/Kolkata"
[285] "Asia/Krasnoyarsk" "Asia/Kuala_Lumpur"
[287] "Asia/Kuching" "Asia/Kuwait"
[289] "Asia/Macao" "Asia/Macau"
[291] "Asia/Magadan" "Asia/Makassar"
[293] "Asia/Manila" "Asia/Muscat"
[295] "Asia/Nicosia" "Asia/Novokuznetsk"
[297] "Asia/Novosibirsk" "Asia/Omsk"
[299] "Asia/Oral" "Asia/Phnom_Penh"
[301] "Asia/Pontianak" "Asia/Pyongyang"
[303] "Asia/Qatar" "Asia/Qostanay"
[305] "Asia/Qyzylorda" "Asia/Rangoon"
[307] "Asia/Riyadh" "Asia/Saigon"
[309] "Asia/Sakhalin" "Asia/Samarkand"
[311] "Asia/Seoul" "Asia/Shanghai"
[313] "Asia/Singapore" "Asia/Srednekolymsk"
[315] "Asia/Taipei" "Asia/Tashkent"
[317] "Asia/Tbilisi" "Asia/Tehran"
[319] "Asia/Tel_Aviv" "Asia/Thimbu"
[321] "Asia/Thimphu" "Asia/Tokyo"
[323] "Asia/Tomsk" "Asia/Ujung_Pandang"
[325] "Asia/Ulaanbaatar" "Asia/Ulan_Bator"
[327] "Asia/Urumqi" "Asia/Ust-Nera"
[329] "Asia/Vientiane" "Asia/Vladivostok"
[331] "Asia/Yakutsk" "Asia/Yangon"
[333] "Asia/Yekaterinburg" "Asia/Yerevan"
[335] "Atlantic/Azores" "Atlantic/Bermuda"
[337] "Atlantic/Canary" "Atlantic/Cape_Verde"
[339] "Atlantic/Faeroe" "Atlantic/Faroe"
[341] "Atlantic/Jan_Mayen" "Atlantic/Madeira"
[343] "Atlantic/Reykjavik" "Atlantic/South_Georgia"
[345] "Atlantic/St_Helena" "Atlantic/Stanley"
[347] "Australia/ACT" "Australia/Adelaide"
[349] "Australia/Brisbane" "Australia/Broken_Hill"
[351] "Australia/Canberra" "Australia/Currie"
[353] "Australia/Darwin" "Australia/Eucla"
[355] "Australia/Hobart" "Australia/LHI"
[357] "Australia/Lindeman" "Australia/Lord_Howe"
[359] "Australia/Melbourne" "Australia/North"
[361] "Australia/NSW" "Australia/Perth"
[363] "Australia/Queensland" "Australia/South"
[365] "Australia/Sydney" "Australia/Tasmania"
[367] "Australia/Victoria" "Australia/West"
[369] "Australia/Yancowinna" "Brazil/Acre"
[371] "Brazil/DeNoronha" "Brazil/East"
[373] "Brazil/West" "Canada/Atlantic"
[375] "Canada/Central" "Canada/Eastern"
[377] "Canada/Mountain" "Canada/Newfoundland"
[379] "Canada/Pacific" "Canada/Saskatchewan"
[381] "Canada/Yukon" "CET"
[383] "Chile/Continental" "Chile/EasterIsland"
[385] "CST6CDT" "Cuba"
[387] "EET" "Egypt"
[389] "Eire" "EST"
[391] "EST5EDT" "Etc/GMT"
[393] "Etc/GMT-0" "Etc/GMT-1"
[395] "Etc/GMT-10" "Etc/GMT-11"
[397] "Etc/GMT-12" "Etc/GMT-13"
[399] "Etc/GMT-14" "Etc/GMT-2"
[401] "Etc/GMT-3" "Etc/GMT-4"
[403] "Etc/GMT-5" "Etc/GMT-6"
[405] "Etc/GMT-7" "Etc/GMT-8"
[407] "Etc/GMT-9" "Etc/GMT+0"
[409] "Etc/GMT+1" "Etc/GMT+10"
[411] "Etc/GMT+11" "Etc/GMT+12"
[413] "Etc/GMT+2" "Etc/GMT+3"
[415] "Etc/GMT+4" "Etc/GMT+5"
[417] "Etc/GMT+6" "Etc/GMT+7"
[419] "Etc/GMT+8" "Etc/GMT+9"
[421] "Etc/GMT0" "Etc/Greenwich"
[423] "Etc/UCT" "Etc/Universal"
[425] "Etc/UTC" "Etc/Zulu"
[427] "Europe/Amsterdam" "Europe/Andorra"
[429] "Europe/Astrakhan" "Europe/Athens"
[431] "Europe/Belfast" "Europe/Belgrade"
[433] "Europe/Berlin" "Europe/Bratislava"
[435] "Europe/Brussels" "Europe/Bucharest"
[437] "Europe/Budapest" "Europe/Busingen"
[439] "Europe/Chisinau" "Europe/Copenhagen"
[441] "Europe/Dublin" "Europe/Gibraltar"
[443] "Europe/Guernsey" "Europe/Helsinki"
[445] "Europe/Isle_of_Man" "Europe/Istanbul"
[447] "Europe/Jersey" "Europe/Kaliningrad"
[449] "Europe/Kiev" "Europe/Kirov"
[451] "Europe/Kyiv" "Europe/Lisbon"
[453] "Europe/Ljubljana" "Europe/London"
[455] "Europe/Luxembourg" "Europe/Madrid"
[457] "Europe/Malta" "Europe/Mariehamn"
[459] "Europe/Minsk" "Europe/Monaco"
[461] "Europe/Moscow" "Europe/Nicosia"
[463] "Europe/Oslo" "Europe/Paris"
[465] "Europe/Podgorica" "Europe/Prague"
[467] "Europe/Riga" "Europe/Rome"
[469] "Europe/Samara" "Europe/San_Marino"
[471] "Europe/Sarajevo" "Europe/Saratov"
[473] "Europe/Simferopol" "Europe/Skopje"
[475] "Europe/Sofia" "Europe/Stockholm"
[477] "Europe/Tallinn" "Europe/Tirane"
[479] "Europe/Tiraspol" "Europe/Ulyanovsk"
[481] "Europe/Uzhgorod" "Europe/Vaduz"
[483] "Europe/Vatican" "Europe/Vienna"
[485] "Europe/Vilnius" "Europe/Volgograd"
[487] "Europe/Warsaw" "Europe/Zagreb"
[489] "Europe/Zaporozhye" "Europe/Zurich"
[491] "GB" "GB-Eire"
[493] "GMT" "GMT-0"
[495] "GMT+0" "GMT0"
[497] "Greenwich" "Hongkong"
[499] "HST" "Iceland"
[501] "Indian/Antananarivo" "Indian/Chagos"
[503] "Indian/Christmas" "Indian/Cocos"
[505] "Indian/Comoro" "Indian/Kerguelen"
[507] "Indian/Mahe" "Indian/Maldives"
[509] "Indian/Mauritius" "Indian/Mayotte"
[511] "Indian/Reunion" "Iran"
[513] "Israel" "Jamaica"
[515] "Japan" "Kwajalein"
[517] "Libya" "MET"
[519] "Mexico/BajaNorte" "Mexico/BajaSur"
[521] "Mexico/General" "MST"
[523] "MST7MDT" "Navajo"
[525] "NZ" "NZ-CHAT"
[527] "Pacific/Apia" "Pacific/Auckland"
[529] "Pacific/Bougainville" "Pacific/Chatham"
[531] "Pacific/Chuuk" "Pacific/Easter"
[533] "Pacific/Efate" "Pacific/Enderbury"
[535] "Pacific/Fakaofo" "Pacific/Fiji"
[537] "Pacific/Funafuti" "Pacific/Galapagos"
[539] "Pacific/Gambier" "Pacific/Guadalcanal"
[541] "Pacific/Guam" "Pacific/Honolulu"
[543] "Pacific/Johnston" "Pacific/Kanton"
[545] "Pacific/Kiritimati" "Pacific/Kosrae"
[547] "Pacific/Kwajalein" "Pacific/Majuro"
[549] "Pacific/Marquesas" "Pacific/Midway"
[551] "Pacific/Nauru" "Pacific/Niue"
[553] "Pacific/Norfolk" "Pacific/Noumea"
[555] "Pacific/Pago_Pago" "Pacific/Palau"
[557] "Pacific/Pitcairn" "Pacific/Pohnpei"
[559] "Pacific/Ponape" "Pacific/Port_Moresby"
[561] "Pacific/Rarotonga" "Pacific/Saipan"
[563] "Pacific/Samoa" "Pacific/Tahiti"
[565] "Pacific/Tarawa" "Pacific/Tongatapu"
[567] "Pacific/Truk" "Pacific/Wake"
[569] "Pacific/Wallis" "Pacific/Yap"
[571] "Poland" "Portugal"
[573] "PRC" "PST8PDT"
[575] "ROC" "ROK"
[577] "Singapore" "Turkey"
[579] "UCT" "Universal"
[581] "US/Alaska" "US/Aleutian"
[583] "US/Arizona" "US/Central"
[585] "US/East-Indiana" "US/Eastern"
[587] "US/Hawaii" "US/Indiana-Starke"
[589] "US/Michigan" "US/Mountain"
[591] "US/Pacific" "US/Samoa"
[593] "UTC" "W-SU"
[595] "WET" "Zulu"
attr(,"Version")
[1] "2023c"と入力してみましょう。
2021aバージョンで593個もタイムゾーンがあるので、目的のものを利用してみてください。
尚、OlsonNamesの関数名が若干覚えにくいので、
?tzstarting httpd help server ... doneと入力すると、説明の途中に、タイムゾーンのリストはOlsonNamesと入力しましょうとでてくるので、とりあえず?tzとだけでも覚えましょう。
あと、今回はTZをJapanとしていますが、私の知る範囲、教科書等では、Asia/Tokyoがタイムゾーンになっていることが多いのでJapanかAsia/Tokyoのどちらかを覚えておくと良いと思います。
最後に、
force_tz(akasi,"UTC")[1] "2000-01-01 09:00:00 UTC"と時刻の表示はそのままでタイムゾーンだけを変化させることも可能なので、必要に応じてご利用ください。