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*.
*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
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
Latitude decimal: Positive is north; negative is south.
Longitude decimal: Positive is east; negative is west.