IANA/Olson Time Zone Offset Search Tool

This timezone search tool lets you look up a time zone from the IANA/Olson timezone database. This calculator is mainly for looking up a historical timezone offset (time difference from UTC/GMT). That is, a timezone offset for a city for a historical date and time. A historical date is any date in the past. This calculator lets you search as far back as the year 1900.

Enter a date, time, and city. It will search the the IANA/Olson timezone database (also known as the tz database). You will get the timezone identifier, the time offset (time difference from UTC/GMT), and the latitude/longitude coordinates of the city. See below for notes*.

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*NOTES: This timezone calculator lets you enter a city, date, and time, and returns the following:

Timezone Identifier:This is obtained via the GeoNames webservices. GeoNames webservice is used to generate the cities list for the calculator. The timezone ID is returned along with the latitude and longitude for the city. (Note that the timezone ID given by GeoNames does not always match the PHP DateTimeZone::listIdentifiers or timezone_identifiers_list. A seperate post will be made listing those discrepancies.)

Time Offset: This is the time difference from UTC/GMT. A positive offset is an East time zone, a negative offset is a West time zone. The time offset is obtained from the PHP DateTime class, using DateTime::getOffset.

Latitude decimal: Positive is north; negative is south.

Longitude decimal: Positive is east; negative is west.

We've One Response

  1. May 19th, 2016 at 1:18 am

    As a part of appreciation regarding providing the very useful application which compares the timezone of different services. I would like to know that does the timezoneId provided by Geonames will be fixed throughout the year considering DST is applicable or not?


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