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Time Zone Detection

AIZAWA Hina edited this page May 8, 2019 · 1 revision

Time Zone Detection estimates your time zone on your first access.
The estimation is done in the following order:

  1. (Restore time zone from cookie)

  2. Estimate the current location from the IP address.
    It also estimates the time zone of the location.
    The GeoIP library is used for this.

  3. Select the time zone according to the display language of the application.
    The display language of the application is obtained from the browser (and/or OS) settings.

Estimate from the IP address

By using the GeoIP library, we can estimate your approximate address from your IP address.
(Note: The address we can obtain here is up to the municipal level, and we will never know your actual location.)

For example, from IP address that assigned to author's home, we can get “Takatsuki, Osaka, Japan, Asia” (34.8586N 135.6061E ± 500km/310mi) with “Asia/Tokyo” time zone. This is just enough accuracy to estimate the time zone, but it is about 10km/6mi away from the home.

If the time zone estimated by GeoIP is “our known time zone”, it will be used as it is. These include Asia/Tokyo, America/New_York, and Europe/Paris.

IANA Identifier's display name
America/Argentina/Buenos_Aires Argentina
Australia/Adelaide Australia (Central)
Australia/Darwin Australia (Central, DST)
Australia/Brisbane Australia (East)
Australia/Sydney Australia (East, DST)
Australia/Perth Australia (West)
America/Belize Belize
America/La_Paz Bolivia
America/Sao_Paulo Brazil (Brasilia)
America/Manaus Brazil (Eastern Amazonas)
America/Noronha Brazil (Fernando de Noronha)
America/Cuiaba Brazil (Mato Grosso)
America/Fortaleza Brazil (Northeastern)
America/Eirunepe Brazil (Western Amazonas)
America/Santiago Chile
Pacific/Easter Chile (Easter Island)
America/Punta_Arenas Chile (Magallanes)
Asia/Shanghai China (PRC)
America/Bogota Colombia
America/Costa_Rica Costa Rica
America/Guayaquil Ecuador
America/El_Salvador El Salvador
Europe/Paris Europe (Central)
Europe/Athens Europe (East)
Europe/London Europe (West)
Pacific/Guam Guam
America/Guatemala Guatemala
America/Guyana Guyana
Pacific/Honolulu Hawaii
America/Tegucigalpa Honduras
Asia/Tokyo Japan
Asia/Seoul Korea
Australia/Lord_Howe Lord Howe Island
America/Mexico_City Mexico (Central)
America/Cancun Mexico (East)
America/Tijuana Mexico (Northwest)
America/Mazatlan Mexico (Pacific)
America/Hermosillo Mexico (Sonora)
America/Managua Nicaragua
America/Adak North America (Adak)
America/Anchorage North America (Alaska)
America/Phoenix North America (Arizona)
America/Halifax North America (AT)
America/Chicago North America (CT)
America/New_York North America (ET)
America/Denver North America (MT)
America/St_Johns North America (Newfoundland)
America/Los_Angeles North America (PT)
America/Regina North America (Saskatchewan)
America/Panama Panama
America/Asuncion Paraguay
America/Lima Peru
Asia/Irkutsk Russia (Irkutsk)
Europe/Kaliningrad Russia (Kaliningrad)
Asia/Kamchatka Russia (Kamchatka)
Asia/Krasnoyarsk Russia (Krasnoyarsk)
Asia/Magadan Russia (Magadan)
Europe/Moscow Russia (Moscow)
Asia/Omsk Russia (Omsk)
Europe/Samara Russia (Samara)
Asia/Vladivostok Russia (Vladivostok)
Asia/Yakutsk Russia (Yakutsk)
Asia/Yekaterinburg Russia (Yekaterinburg)
America/Paramaribo Suriname
Asia/Taipei Taiwan
America/Montevideo Uruguay
America/Caracas Venezuela
Asia/Urumqi Xinjiang

Unfortunately, GeoIP returns more than just the time zones listed above.
So, if we don't have, we will guess what's “perhaps correct.”

For example, if GeoIP returns Europe/Berlin, we guess “Central European Time (Europe/Paris).”

Problems such as Russia being selected in Central Asia will occur, but it will often work.
Minor daylight saving time (summer time) rules can cause minor problems.
In either case, you can require the administrator to add a time zone configuration.

If the system cannot find a substitutable time zone, the system may adopt an “offset from UTC” such as Etc/UTC-9.
In this format, 30 minutes offset can not be expressed. We will be required to add a new time zone.

Estimate from application language

The rule above should determine the time zone in almost all cases, but it is a mechanism provided just in case.

The system sets the following time zone according to the specified or detected language:

Language Time zone
Deutsch Europe/Paris
English (UK) Europe/London
English (US) America/Los_Angeles
Español (ES) Europe/Paris
Español (MX) America/Mexico_City
Français (FR) Europe/Paris
Français (CA) America/New_York
Italiano Europe/Paris
Nederlands Europe/Paris
Русский Europe/Moscow
日本語 Asia/Tokyo

This is a last resort.

Request for time zone addition

If necessary, you can request us to add a time zone.
Typically, there is no suitable time zone or when special daylight savings time (summer time) responses are required.

We are not as detailed as you about the time zones of your country.
Please tell us about your country's time zones.

  • Region in the world (e.g. “East Asia”, “North America”)
  • Country (or region) Name (e.g. “Japan”, “United States”)
  • Time zones (please tell us all time zones if possible if divided into multiple TZs.)
    • Name (e.g. “Japan”, “Pacific Time”, “Arizona”)
    • IANA Time zone identifier (e.g. “Asia/Tokyo”, “America/Los_Angeles”, “America/Phoenix”)
You can’t perform that action at this time.