unknown timezone name in R strptime/as.POSIXct

Question

Where can I find a list of all legal time names for R function as.POSIXct?

as.POSIXct(\"1970-01-01\",tz=\"CST\") generates a warning that \

Answer 1

TL;DR: Set the tz option with this command to make the warning go away

options(tz="Asia/Seoul") # Set to appropriate timezone

Now a timezone is set in your R session and the warning will disappear. Use OlsonNames() to see a full list of timezones you can use (or scroll down for full list below).

---

Related info

If options("tz") returns NULL that means no timezone has been set for the current R session:

options("tz")
$tz
NULL

View the currently set timezone option with options("tz")

options(tz="Asia/Seoul") 
options("tz")
$tz
[1] "Asia/Seoul"

Here is a full list of timezones. You can generate the list with the OlsonNames() command.

OlsonNames()
  [1] "Africa/Abidjan"                  
  [2] "Africa/Accra"                    
  [3] "Africa/Addis_Ababa"              
  [4] "Africa/Algiers"                  
  [5] "Africa/Asmara"                   
  [6] "Africa/Asmera"                   
  [7] "Africa/Bamako"                   
  [8] "Africa/Bangui"                   
  [9] "Africa/Banjul"                   
 [10] "Africa/Bissau"                   
 [11] "Africa/Blantyre"                 
 [12] "Africa/Brazzaville"              
 [13] "Africa/Bujumbura"                
 [14] "Africa/Cairo"                    
 [15] "Africa/Casablanca"               
 [16] "Africa/Ceuta"                    
 [17] "Africa/Conakry"                  
 [18] "Africa/Dakar"                    
 [19] "Africa/Dar_es_Salaam"            
 [20] "Africa/Djibouti"                 
 [21] "Africa/Douala"                   
 [22] "Africa/El_Aaiun"                 
 [23] "Africa/Freetown"                 
 [24] "Africa/Gaborone"                 
 [25] "Africa/Harare"                   
 [26] "Africa/Johannesburg"             
 [27] "Africa/Juba"                     
 [28] "Africa/Kampala"                  
 [29] "Africa/Khartoum"                 
 [30] "Africa/Kigali"                   
 [31] "Africa/Kinshasa"                 
 [32] "Africa/Lagos"                    
 [33] "Africa/Libreville"               
 [34] "Africa/Lome"                     
 [35] "Africa/Luanda"                   
 [36] "Africa/Lubumbashi"               
 [37] "Africa/Lusaka"                   
 [38] "Africa/Malabo"                   
 [39] "Africa/Maputo"                   
 [40] "Africa/Maseru"                   
 [41] "Africa/Mbabane"                  
 [42] "Africa/Mogadishu"                
 [43] "Africa/Monrovia"                 
 [44] "Africa/Nairobi"                  
 [45] "Africa/Ndjamena"                 
 [46] "Africa/Niamey"                   
 [47] "Africa/Nouakchott"               
 [48] "Africa/Ouagadougou"              
 [49] "Africa/Porto-Novo"               
 [50] "Africa/Sao_Tome"                 
 [51] "Africa/Timbuktu"                 
 [52] "Africa/Tripoli"                  
 [53] "Africa/Tunis"                    
 [54] "Africa/Windhoek"                 
 [55] "America/Adak"                    
 [56] "America/Anchorage"               
 [57] "America/Anguilla"                
 [58] "America/Antigua"                 
 [59] "America/Araguaina"               
 [60] "America/Argentina/Buenos_Aires"  
 [61] "America/Argentina/Catamarca"     
 [62] "America/Argentina/ComodRivadavia"
 [63] "America/Argentina/Cordoba"       
 [64] "America/Argentina/Jujuy"         
 [65] "America/Argentina/La_Rioja"      
 [66] "America/Argentina/Mendoza"       
 [67] "America/Argentina/Rio_Gallegos"  
 [68] "America/Argentina/Salta"         
 [69] "America/Argentina/San_Juan"      
 [70] "America/Argentina/San_Luis"      
 [71] "America/Argentina/Tucuman"       
 [72] "America/Argentina/Ushuaia"       
 [73] "America/Aruba"                   
 [74] "America/Asuncion"                
 [75] "America/Atikokan"                
 [76] "America/Atka"                    
 [77] "America/Bahia"                   
 [78] "America/Bahia_Banderas"          
 [79] "America/Barbados"                
 [80] "America/Belem"                   
 [81] "America/Belize"                  
 [82] "America/Blanc-Sablon"            
 [83] "America/Boa_Vista"               
 [84] "America/Bogota"                  
 [85] "America/Boise"                   
 [86] "America/Buenos_Aires"            
 [87] "America/Cambridge_Bay"           
 [88] "America/Campo_Grande"            
 [89] "America/Cancun"                  
 [90] "America/Caracas"                 
 [91] "America/Catamarca"               
 [92] "America/Cayenne"                 
 [93] "America/Cayman"                  
 [94] "America/Chicago"                 
 [95] "America/Chihuahua"               
 [96] "America/Coral_Harbour"           
 [97] "America/Cordoba"                 
 [98] "America/Costa_Rica"              
 [99] "America/Creston"                 
[100] "America/Cuiaba"                  
[101] "America/Curacao"                 
[102] "America/Danmarkshavn"            
[103] "America/Dawson"                  
[104] "America/Dawson_Creek"            
[105] "America/Denver"                  
[106] "America/Detroit"                 
[107] "America/Dominica"                
[108] "America/Edmonton"                
[109] "America/Eirunepe"                
[110] "America/El_Salvador"             
[111] "America/Ensenada"                
[112] "America/Fort_Nelson"             
[113] "America/Fort_Wayne"              
[114] "America/Fortaleza"               
[115] "America/Glace_Bay"               
[116] "America/Godthab"                 
[117] "America/Goose_Bay"               
[118] "America/Grand_Turk"              
[119] "America/Grenada"                 
[120] "America/Guadeloupe"              
[121] "America/Guatemala"               
[122] "America/Guayaquil"               
[123] "America/Guyana"                  
[124] "America/Halifax"                 
[125] "America/Havana"                  
[126] "America/Hermosillo"              
[127] "America/Indiana/Indianapolis"    
[128] "America/Indiana/Knox"            
[129] "America/Indiana/Marengo"         
[130] "America/Indiana/Petersburg"      
[131] "America/Indiana/Tell_City"       
[132] "America/Indiana/Vevay"           
[133] "America/Indiana/Vincennes"       
[134] "America/Indiana/Winamac"         
[135] "America/Indianapolis"            
[136] "America/Inuvik"                  
[137] "America/Iqaluit"                 
[138] "America/Jamaica"                 
[139] "America/Jujuy"                   
[140] "America/Juneau"                  
[141] "America/Kentucky/Louisville"     
[142] "America/Kentucky/Monticello"     
[143] "America/Knox_IN"                 
[144] "America/Kralendijk"              
[145] "America/La_Paz"                  
[146] "America/Lima"                    
[147] "America/Los_Angeles"             
[148] "America/Louisville"              
[149] "America/Lower_Princes"           
[150] "America/Maceio"                  
[151] "America/Managua"                 
[152] "America/Manaus"                  
[153] "America/Marigot"                 
[154] "America/Martinique"              
[155] "America/Matamoros"               
[156] "America/Mazatlan"                
[157] "America/Mendoza"                 
[158] "America/Menominee"               
[159] "America/Merida"                  
[160] "America/Metlakatla"              
[161] "America/Mexico_City"             
[162] "America/Miquelon"                
[163] "America/Moncton"                 
[164] "America/Monterrey"               
[165] "America/Montevideo"              
[166] "America/Montreal"                
[167] "America/Montserrat"              
[168] "America/Nassau"                  
[169] "America/New_York"                
[170] "America/Nipigon"                 
[171] "America/Nome"                    
[172] "America/Noronha"                 
[173] "America/North_Dakota/Beulah"     
[174] "America/North_Dakota/Center"     
[175] "America/North_Dakota/New_Salem"  
[176] "America/Nuuk"                    
[177] "America/Ojinaga"                 
[178] "America/Panama"                  
[179] "America/Pangnirtung"             
[180] "America/Paramaribo"              
[181] "America/Phoenix"                 
[182] "America/Port_of_Spain"           
[183] "America/Port-au-Prince"          
[184] "America/Porto_Acre"              
[185] "America/Porto_Velho"             
[186] "America/Puerto_Rico"             
[187] "America/Punta_Arenas"            
[188] "America/Rainy_River"             
[189] "America/Rankin_Inlet"            
[190] "America/Recife"                  
[191] "America/Regina"                  
[192] "America/Resolute"                
[193] "America/Rio_Branco"              
[194] "America/Rosario"                 
[195] "America/Santa_Isabel"            
[196] "America/Santarem"                
[197] "America/Santiago"                
[198] "America/Santo_Domingo"           
[199] "America/Sao_Paulo"               
[200] "America/Scoresbysund"            
[201] "America/Shiprock"                
[202] "America/Sitka"                   
[203] "America/St_Barthelemy"           
[204] "America/St_Johns"                
[205] "America/St_Kitts"                
[206] "America/St_Lucia"                
[207] "America/St_Thomas"               
[208] "America/St_Vincent"              
[209] "America/Swift_Current"           
[210] "America/Tegucigalpa"             
[211] "America/Thule"                   
[212] "America/Thunder_Bay"             
[213] "America/Tijuana"                 
[214] "America/Toronto"                 
[215] "America/Tortola"                 
[216] "America/Vancouver"               
[217] "America/Virgin"                  
[218] "America/Whitehorse"              
[219] "America/Winnipeg"                
[220] "America/Yakutat"                 
[221] "America/Yellowknife"             
[222] "Antarctica/Casey"                
[223] "Antarctica/Davis"                
[224] "Antarctica/DumontDUrville"       
[225] "Antarctica/Macquarie"            
[226] "Antarctica/Mawson"               
[227] "Antarctica/McMurdo"              
[228] "Antarctica/Palmer"               
[229] "Antarctica/Rothera"              
[230] "Antarctica/South_Pole"           
[231] "Antarctica/Syowa"                
[232] "Antarctica/Troll"                
[233] "Antarctica/Vostok"               
[234] "Arctic/Longyearbyen"             
[235] "Asia/Aden"                       
[236] "Asia/Almaty"                     
[237] "Asia/Amman"                      
[238] "Asia/Anadyr"                     
[239] "Asia/Aqtau"                      
[240] "Asia/Aqtobe"                     
[241] "Asia/Ashgabat"                   
[242] "Asia/Ashkhabad"                  
[243] "Asia/Atyrau"                     
[244] "Asia/Baghdad"                    
[245] "Asia/Bahrain"                    
[246] "Asia/Baku"                       
[247] "Asia/Bangkok"                    
[248] "Asia/Barnaul"                    
[249] "Asia/Beirut"                     
[250] "Asia/Bishkek"                    
[251] "Asia/Brunei"                     
[252] "Asia/Calcutta"                   
[253] "Asia/Chita"                      
[254] "Asia/Choibalsan"                 
[255] "Asia/Chongqing"                  
[256] "Asia/Chungking"                  
[257] "Asia/Colombo"                    
[258] "Asia/Dacca"                      
[259] "Asia/Damascus"                   
[260] "Asia/Dhaka"                      
[261] "Asia/Dili"                       
[262] "Asia/Dubai"                      
[263] "Asia/Dushanbe"                   
[264] "Asia/Famagusta"                  
[265] "Asia/Gaza"                       
[266] "Asia/Harbin"                     
[267] "Asia/Hebron"                     
[268] "Asia/Ho_Chi_Minh"                
[269] "Asia/Hong_Kong"                  
[270] "Asia/Hovd"                       
[271] "Asia/Irkutsk"                    
[272] "Asia/Istanbul"                   
[273] "Asia/Jakarta"                    
[274] "Asia/Jayapura"                   
[275] "Asia/Jerusalem"                  
[276] "Asia/Kabul"                      
[277] "Asia/Kamchatka"                  
[278] "Asia/Karachi"                    
[279] "Asia/Kashgar"                    
[280] "Asia/Kathmandu"                  
[281] "Asia/Katmandu"                   
[282] "Asia/Khandyga"                   
[283] "Asia/Kolkata"                    
[284] "Asia/Krasnoyarsk"                
[285] "Asia/Kuala_Lumpur"               
[286] "Asia/Kuching"                    
[287] "Asia/Kuwait"                     
[288] "Asia/Macao"                      
[289] "Asia/Macau"                      
[290] "Asia/Magadan"                    
[291] "Asia/Makassar"                   
[292] "Asia/Manila"                     
[293] "Asia/Muscat"                     
[294] "Asia/Nicosia"                    
[295] "Asia/Novokuznetsk"               
[296] "Asia/Novosibirsk"                
[297] "Asia/Omsk"                       
[298] "Asia/Oral"                       
[299] "Asia/Phnom_Penh"                 
[300] "Asia/Pontianak"                  
[301] "Asia/Pyongyang"                  
[302] "Asia/Qatar"                      
[303] "Asia/Qostanay"                   
[304] "Asia/Qyzylorda"                  
[305] "Asia/Rangoon"                    
[306] "Asia/Riyadh"                     
[307] "Asia/Saigon"                     
[308] "Asia/Sakhalin"                   
[309] "Asia/Samarkand"                  
[310] "Asia/Seoul"                      
[311] "Asia/Shanghai"                   
[312] "Asia/Singapore"                  
[313] "Asia/Srednekolymsk"              
[314] "Asia/Taipei"                     
[315] "Asia/Tashkent"                   
[316] "Asia/Tbilisi"                    
[317] "Asia/Tehran"                     
[318] "Asia/Tel_Aviv"                   
[319] "Asia/Thimbu"                     
[320] "Asia/Thimphu"                    
[321] "Asia/Tokyo"                      
[322] "Asia/Tomsk"                      
[323] "Asia/Ujung_Pandang"              
[324] "Asia/Ulaanbaatar"                
[325] "Asia/Ulan_Bator"                 
[326] "Asia/Urumqi"                     
[327] "Asia/Ust-Nera"                   
[328] "Asia/Vientiane"                  
[329] "Asia/Vladivostok"                
[330] "Asia/Yakutsk"                    
[331] "Asia/Yangon"                     
[332] "Asia/Yekaterinburg"              
[333] "Asia/Yerevan"                    
[334] "Atlantic/Azores"                 
[335] "Atlantic/Bermuda"                
[336] "Atlantic/Canary"                 
[337] "Atlantic/Cape_Verde"             
[338] "Atlantic/Faeroe"                 
[339] "Atlantic/Faroe"                  
[340] "Atlantic/Jan_Mayen"              
[341] "Atlantic/Madeira"                
[342] "Atlantic/Reykjavik"              
[343] "Atlantic/South_Georgia"          
[344] "Atlantic/St_Helena"              
[345] "Atlantic/Stanley"                
[346] "Australia/ACT"                   
[347] "Australia/Adelaide"              
[348] "Australia/Brisbane"              
[349] "Australia/Broken_Hill"           
[350] "Australia/Canberra"              
[351] "Australia/Currie"                
[352] "Australia/Darwin"                
[353] "Australia/Eucla"                 
[354] "Australia/Hobart"                
[355] "Australia/LHI"                   
[356] "Australia/Lindeman"              
[357] "Australia/Lord_Howe"             
[358] "Australia/Melbourne"             
[359] "Australia/North"                 
[360] "Australia/NSW"                   
[361] "Australia/Perth"                 
[362] "Australia/Queensland"            
[363] "Australia/South"                 
[364] "Australia/Sydney"                
[365] "Australia/Tasmania"              
[366] "Australia/Victoria"              
[367] "Australia/West"                  
[368] "Australia/Yancowinna"            
[369] "Brazil/Acre"                     
[370] "Brazil/DeNoronha"                
[371] "Brazil/East"                     
[372] "Brazil/West"                     
[373] "Canada/Atlantic"                 
[374] "Canada/Central"                  
[375] "Canada/Eastern"                  
[376] "Canada/Mountain"                 
[377] "Canada/Newfoundland"             
[378] "Canada/Pacific"                  
[379] "Canada/Saskatchewan"             
[380] "Canada/Yukon"                    
[381] "CET"                             
[382] "Chile/Continental"               
[383] "Chile/EasterIsland"              
[384] "CST6CDT"                         
[385] "Cuba"                            
[386] "EET"                             
[387] "Egypt"                           
[388] "Eire"                            
[389] "EST"                             
[390] "EST5EDT"                         
[391] "Etc/GMT"                         
[392] "Etc/GMT-0"                       
[393] "Etc/GMT-1"                       
[394] "Etc/GMT-10"                      
[395] "Etc/GMT-11"                      
[396] "Etc/GMT-12"                      
[397] "Etc/GMT-13"                      
[398] "Etc/GMT-14"                      
[399] "Etc/GMT-2"                       
[400] "Etc/GMT-3"                       
[401] "Etc/GMT-4"                       
[402] "Etc/GMT-5"                       
[403] "Etc/GMT-6"                       
[404] "Etc/GMT-7"                       
[405] "Etc/GMT-8"                       
[406] "Etc/GMT-9"                       
[407] "Etc/GMT+0"                       
[408] "Etc/GMT+1"                       
[409] "Etc/GMT+10"                      
[410] "Etc/GMT+11"                      
[411] "Etc/GMT+12"                      
[412] "Etc/GMT+2"                       
[413] "Etc/GMT+3"                       
[414] "Etc/GMT+4"                       
[415] "Etc/GMT+5"                       
[416] "Etc/GMT+6"                       
[417] "Etc/GMT+7"                       
[418] "Etc/GMT+8"                       
[419] "Etc/GMT+9"                       
[420] "Etc/GMT0"                        
[421] "Etc/Greenwich"                   
[422] "Etc/UCT"                         
[423] "Etc/Universal"                   
[424] "Etc/UTC"                         
[425] "Etc/Zulu"                        
[426] "Europe/Amsterdam"                
[427] "Europe/Andorra"                  
[428] "Europe/Astrakhan"                
[429] "Europe/Athens"                   
[430] "Europe/Belfast"                  
[431] "Europe/Belgrade"                 
[432] "Europe/Berlin"                   
[433] "Europe/Bratislava"               
[434] "Europe/Brussels"                 
[435] "Europe/Bucharest"                
[436] "Europe/Budapest"                 
[437] "Europe/Busingen"                 
[438] "Europe/Chisinau"                 
[439] "Europe/Copenhagen"               
[440] "Europe/Dublin"                   
[441] "Europe/Gibraltar"                
[442] "Europe/Guernsey"                 
[443] "Europe/Helsinki"                 
[444] "Europe/Isle_of_Man"              
[445] "Europe/Istanbul"                 
[446] "Europe/Jersey"                   
[447] "Europe/Kaliningrad"              
[448] "Europe/Kiev"                     
[449] "Europe/Kirov"                    
[450] "Europe/Lisbon"                   
[451] "Europe/Ljubljana"                
[452] "Europe/London"                   
[453] "Europe/Luxembourg"               
[454] "Europe/Madrid"                   
[455] "Europe/Malta"                    
[456] "Europe/Mariehamn"                
[457] "Europe/Minsk"                    
[458] "Europe/Monaco"                   
[459] "Europe/Moscow"                   
[460] "Europe/Nicosia"                  
[461] "Europe/Oslo"                     
[462] "Europe/Paris"                    
[463] "Europe/Podgorica"                
[464] "Europe/Prague"                   
[465] "Europe/Riga"                     
[466] "Europe/Rome"                     
[467] "Europe/Samara"                   
[468] "Europe/San_Marino"               
[469] "Europe/Sarajevo"                 
[470] "Europe/Saratov"                  
[471] "Europe/Simferopol"               
[472] "Europe/Skopje"                   
[473] "Europe/Sofia"                    
[474] "Europe/Stockholm"                
[475] "Europe/Tallinn"                  
[476] "Europe/Tirane"                   
[477] "Europe/Tiraspol"                 
[478] "Europe/Ulyanovsk"                
[479] "Europe/Uzhgorod"                 
[480] "Europe/Vaduz"                    
[481] "Europe/Vatican"                  
[482] "Europe/Vienna"                   
[483] "Europe/Vilnius"                  
[484] "Europe/Volgograd"                
[485] "Europe/Warsaw"                   
[486] "Europe/Zagreb"                   
[487] "Europe/Zaporozhye"               
[488] "Europe/Zurich"                   
[489] "GB"                              
[490] "GB-Eire"                         
[491] "GMT"                             
[492] "GMT-0"                           
[493] "GMT+0"                           
[494] "GMT0"                            
[495] "Greenwich"                       
[496] "Hongkong"                        
[497] "HST"                             
[498] "Iceland"                         
[499] "Indian/Antananarivo"             
[500] "Indian/Chagos"                   
[501] "Indian/Christmas"                
[502] "Indian/Cocos"                    
[503] "Indian/Comoro"                   
[504] "Indian/Kerguelen"                
[505] "Indian/Mahe"                     
[506] "Indian/Maldives"                 
[507] "Indian/Mauritius"                
[508] "Indian/Mayotte"                  
[509] "Indian/Reunion"                  
[510] "Iran"                            
[511] "Israel"                          
[512] "Jamaica"                         
[513] "Japan"                           
[514] "Kwajalein"                       
[515] "Libya"                           
[516] "MET"                             
[517] "Mexico/BajaNorte"                
[518] "Mexico/BajaSur"                  
[519] "Mexico/General"                  
[520] "MST"                             
[521] "MST7MDT"                         
[522] "Navajo"                          
[523] "NZ"                              
[524] "NZ-CHAT"                         
[525] "Pacific/Apia"                    
[526] "Pacific/Auckland"                
[527] "Pacific/Bougainville"            
[528] "Pacific/Chatham"                 
[529] "Pacific/Chuuk"                   
[530] "Pacific/Easter"                  
[531] "Pacific/Efate"                   
[532] "Pacific/Enderbury"               
[533] "Pacific/Fakaofo"                 
[534] "Pacific/Fiji"                    
[535] "Pacific/Funafuti"                
[536] "Pacific/Galapagos"               
[537] "Pacific/Gambier"                 
[538] "Pacific/Guadalcanal"             
[539] "Pacific/Guam"                    
[540] "Pacific/Honolulu"                
[541] "Pacific/Johnston"                
[542] "Pacific/Kiritimati"              
[543] "Pacific/Kosrae"                  
[544] "Pacific/Kwajalein"               
[545] "Pacific/Majuro"                  
[546] "Pacific/Marquesas"               
[547] "Pacific/Midway"                  
[548] "Pacific/Nauru"                   
[549] "Pacific/Niue"                    
[550] "Pacific/Norfolk"                 
[551] "Pacific/Noumea"                  
[552] "Pacific/Pago_Pago"               
[553] "Pacific/Palau"                   
[554] "Pacific/Pitcairn"                
[555] "Pacific/Pohnpei"                 
[556] "Pacific/Ponape"                  
[557] "Pacific/Port_Moresby"            
[558] "Pacific/Rarotonga"               
[559] "Pacific/Saipan"                  
[560] "Pacific/Samoa"                   
[561] "Pacific/Tahiti"                  
[562] "Pacific/Tarawa"                  
[563] "Pacific/Tongatapu"               
[564] "Pacific/Truk"                    
[565] "Pacific/Wake"                    
[566] "Pacific/Wallis"                  
[567] "Pacific/Yap"                     
[568] "Poland"                          
[569] "Portugal"                        
[570] "PRC"                             
[571] "PST8PDT"                         
[572] "ROC"                             
[573] "ROK"                             
[574] "Singapore"                       
[575] "Turkey"                          
[576] "UCT"                             
[577] "Universal"                       
[578] "US/Alaska"                       
[579] "US/Aleutian"                     
[580] "US/Arizona"                      
[581] "US/Central"                      
[582] "US/East-Indiana"                 
[583] "US/Eastern"                      
[584] "US/Hawaii"                       
[585] "US/Indiana-Starke"               
[586] "US/Michigan"                     
[587] "US/Mountain"                     
[588] "US/Pacific"                      
[589] "US/Pacific-New"                  
[590] "US/Samoa"                        
[591] "UTC"                             
[592] "W-SU"                            
[593] "WET"                             
[594] "Zulu"                            
attr(,"Version")
[1] "2020a"

Answer 2

Most R platforms use the time-zone database compiled by David Olson, where the preferred reference is by location. There names are a bit outdated but they will help you get going.

Find a full list of available time zones (doesn't work on windows):

OlsonNames()

For folks running windows that OlsonNames() doesn't work: See the full list here.

Or read up in more detail here http://www.twinsun.com/tz/tz-link.htm

Answer 3

?Sys.timezone has some hints, specifically to look in: "R_HOME/share/zoneinfo/zone.tab" (R_HOME is the directory R is installed in). Keep in mind that time zones are nasty and many of their nuances are operating system (and locale?) specific.

In your specific case, you want "CST6CDT" instead of "CST".

Answer 4

Timezone stuff can drive you NUTS!!

Being located in Germany, this is what I used to do to set my tz:

> options(tz="Europe/Berlin")

Doing so, I always wondered why R would throw "unknown timezone" warnings:

> t <- "2011-11-08 09:42:00"
> as.POSIXct(t, tz=getOption("tz"))
[1] "2011-11-08 09:42:00 CET"
Warning messages:
1: In strptime(xx, f <- "%Y-%m-%d %H:%M:%OS", tz = tz) :
  unknown timezone 'MET-1MST'
2: In as.POSIXct.POSIXlt(x) : unknown timezone 'MET-1MST'
3: In strptime(x, f, tz = tz) : unknown timezone 'MET-1MST'
4: In as.POSIXct.POSIXlt(as.POSIXlt(x, tz, ...), tz, ...) :
  unknown timezone 'MET-1MST'
5: In as.POSIXlt.POSIXct(x, tz) : unknown timezone 'MET-1MST'

Someday I found out that setting tz via options() was not enough as the environment variable TZ is not affected and hence all the the trouble:

> Sys.getenv("TZ")
[1] "MET-1MST"

Changing this should do away with the nasty warnings:

> Sys.setenv(TZ="Europe/Berlin")
> Sys.getenv("TZ")
[1] "Europe/Berlin"
> as.POSIXct(t, tz=getOption("tz"))
[1] "2011-11-08 09:42:00 CET"

Answer 5

Couldn't find it in that location on my make but found a zipped version in a source directory. Here's a list of timezone abbreviations that appear at the top level of the zones.tab file:

CET, CST6CDT, Cuba, EET, EST, EST5EDT, Egypt, Eire, Factory, GB, GB-Eire, GMT,
GMT+0, GMT-0, GMT0, Greenwich, HST, Hongkong, Iceland, Iran, Israel, Jamaica, Japan,
Kwajalein, Libya, MET, MST, MST7MDT, NZ, NZ-CHAT, Navajo, PRC, PST8PDT, Poland, Portugal,
ROC, ROK, Singapore, Turkey, UCT, UTC, Universal, W-SU, WET, Zulu

There are also folders with continent/country names, which have more options such as the America/New_York example above.:

Africa/     Asia/       Canada/     Indian/
America/    Atlantic/   Chile/      Mexico/
Antarctica/ Australia/  Etc/        Pacific/
Arctic/     Brazil/     Europe/     US/

This was found in the /R-2.11.1/src/extra/tzone/zoneinfo.zip file.