TZInfo - Ruby Timezone Library

TZInfo provides daylight savings aware transformations between times in different timezones.

Data Sources

TZInfo requires a source of timezone data. There are two built-in options:

  1. The TZInfo::Data library (the tzinfo-data gem). TZInfo::Data contains a set of Ruby modules that are generated from the IANA Time Zone Database.
  2. A zoneinfo directory. Most Unix-like systems include a zoneinfo directory containing timezone definitions. These are also generated from the IANA Time Zone Database.

By default, TZInfo::Data will be used. If TZInfo::Data is not available (i.e. if require 'tzinfo/data' fails), then TZInfo will search for a zoneinfo directory instead (using the search path specified by TZInfo::ZoneinfoDataSource::DEFAULT_SEARCH_PATH).

If no data source can be found, a TZInfo::DataSourceNotFound exception will be raised when TZInfo is used.

The default data source selection can be overridden using TZInfo::DataSource.set.

Custom data sources can also be used. See TZInfo::DataSource.set for further details.


The TZInfo gem can be installed by running:

gem install tzinfo

To use the Ruby modules as the data source, TZInfo::Data will also need to be installed:

gem install tzinfo-data

Example Usage

The following code will obtain the America/New_York timezone (as an instance of TZInfo::Timezone) and covert a time in UTC to local New York time:

require 'tzinfo'

tz = TZInfo::Timezone.get('America/New_York')
local = tz.utc_to_local(Time.utc(2005,8,29,15,35,0))

Note that the local Time returned will have a UTC timezone ( will return "UTC"). This is because the Ruby Time class only supports two timezones: UTC and the current system local timezone.

To convert from a local time to UTC, the local_to_utc method can be used as follows:

utc = tz.local_to_utc(local)

Note that the timezone information of the local Time object is ignored (TZInfo will just read the date and time and treat them as if there were in the 'tz' timezone). The following two lines will return the same result regardless of the system's local timezone:


To obtain information about the rules in force at a particular UTC or local time, the TZInfo::Timezone.period_for_utc and TZInfo::Timezone.period_for_local methods can be used. Both of these methods return TZInfo::TimezonePeriod objects. The following gets the identifier for the period (in this case EDT).

period = tz.period_for_utc(Time.utc(2005,8,29,15,35,0))
id = period.zone_identifier

The current local time in a Timezone can be obtained with the TZInfo::Timezone#now method:

now =

All methods in TZInfo that operate on a time can be used with either Time or DateTime instances or with Integer timestamps (i.e. as returned by Time#to_i). The type of the values returned will match the the type passed in.

A list of all the available Timezone identifiers can be obtained using the TZInfo::Timezone.all_identifiers method. TZInfo::Timezone.all can be called to get an Array of all the TZInfo::Timezone instances.

Timezones can also be accessed by country (using an ISO 3166-1 alpha-2 country code). The following code retrieves the TZInfo::Country instance representing the USA (country code 'US') and then gets all the Timezone identifiers used in the USA.

us = TZInfo::Country.get('US')
timezones = us.zone_identifiers

The TZInfo::Country#zone_info method provides an additional description and geographic location for each Timezone in a Country.

A list of all the available country codes can be obtained using the TZInfo::Country.all_codes method. TZInfo::Country.all can be called to get an Array of all the Country instances.

For further detail, please refer to the API documentation for the TZInfo::Timezone and TZInfo::Country classes.


The TZInfo::Country and TZInfo::Timezone classes are thread-safe. It is safe to use class and instance methods of TZInfo::Country and TZInfo::Timezone in concurrently executing threads. Instances of both classes can be shared across thread boundaries.


API documentation for TZInfo is available on


TZInfo is released under the MIT license, see LICENSE for details.

Source Code

Source code for TZInfo is available on GitHub.

Issue Tracker

Please post any bugs, issues, feature requests or questions to the GitHub issue tracker.