TZInfo provides daylight savings aware transformations between times in different timezones.
TZInfo requires a source of timezone data. There are two built-in options:
- 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.
- 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. Further information is available
in the wiki to help with
resolving TZInfo::DataSourceNotFound errors.
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
The following code will obtain the America/New_York timezone (as an instance
of TZInfo::Timezone) and convert 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 (local.zone 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:
tz.local_to_utc(Time.local(2006,6,26,1,0,0))
tz.local_to_utc(Time.utc(2006,6,26,1,0,0))
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 = tz.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 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 RubyDoc.info.
TZInfo is released under the MIT license, see LICENSE for details.
Source code for TZInfo is available on GitHub.
Please post any bugs, issues, feature requests or questions to the GitHub issue tracker.