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TZInfo - Ruby Timezone Library
https://github.com/tzinfo/tzinfo

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TZInfo - Ruby Timezone Library

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# TZInfo - Ruby Time Zone Library



[![RubyGems](https://img.shields.io/gem/v/tzinfo?logo=rubygems&label=Gem)](https://rubygems.org/gems/tzinfo) [![Tests](https://github.com/tzinfo/tzinfo/workflows/Tests/badge.svg?branch=master&event=push)](https://github.com/tzinfo/tzinfo/actions?query=workflow%3ATests+branch%3Amaster+event%3Apush)



[TZInfo](https://tzinfo.github.io) is a Ruby library that provides access to

time zone data and allows times to be converted using time zone rules.



## Data Sources



TZInfo requires a source of time zone data. There are two options:



1. A zoneinfo directory containing timezone definition files. These files are

   generated from the [IANA Time Zone Database](https://www.iana.org/time-zones)

   using the `zic` utility. Most Unix-like systems include a zoneinfo directory.

2. The TZInfo::Data library (the tzinfo-data gem). TZInfo::Data contains a set

   of Ruby modules that are also generated from the IANA Time Zone Database.



By default, TZInfo will attempt to use TZInfo::Data. If TZInfo::Data is not

available (i.e. if `require 'tzinfo/data'` fails), then TZInfo will search for a

zoneinfo directory instead (by checking the directories specified by

`TZInfo::DataSources::ZoneinfoDataSource.search_path` in turn).



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](https://tzinfo.github.io/datasourcenotfound) to help resolve

`TZInfo::DataSourceNotFound` errors.



The default data source selection can be overridden by calling

`TZInfo::DataSource.set`.



Custom data sources can also be used. See the `TZInfo::DataSource.set`

documentation for further details.



## Installation



The TZInfo gem can be installed by running `gem install tzinfo` or by adding

`gem 'tzinfo'` to your `Gemfile` and running `bundle install`.



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

installed by running `gem install tzinfo-data` or by adding `gem 'tzinfo-data'`

to your `Gemfile`.



## IANA Time Zone Database



The data returned and used by TZInfo is sourced from the

[IANA Time Zone Database](https://www.iana.org/time-zones). The

[Theory and pragmatics of the tz code and data](https://data.iana.org/time-zones/theory.html)

document gives details of how the data is organized and managed.



## Example Usage



To use TZInfo, it must first be required with:



```ruby

require 'tzinfo'

```



The `TZInfo::Timezone` class provides access to time zone data and methods for

converting times.



The `all_identifiers` method returns a list of valid time zone identifiers:



```ruby

identifiers = TZInfo::Timezone.all_identifiers

# => ["Africa/Adibdjan", "Africa/Accra", ..., "Zulu"]

```



A `TZInfo::Timezone` instance representing an individual time zone can be

obtained with `TZInfo::Timezone.get`:



```ruby

tz = TZInfo::Timezone.get('America/New_York')

# => #

```



A time can be converted to the local time of the time zone with `to_local`:



```ruby

tz.to_local(Time.utc(2018, 2, 1, 12, 30, 0))

# => 2018-02-01 07:30:00 -0500

tz.to_local(Time.utc(2018, 7, 1, 12, 30, 0))

# => 2018-07-01 08:30:00 -0400

tz.to_local(Time.new(2018, 7, 1, 13, 30, 0, '+01:00'))

# => 2018-07-01 08:30:00 -0400

```



Local times with the appropriate offset for the time zone can be constructed

with `local_time`:



```ruby

tz.local_time(2018, 2, 1, 7, 30, 0)

# => 2018-02-01 07:30:00 -0500

tz.local_time(2018, 7, 1, 8, 30, 0)

# => 2018-07-01 08:30:00 -0400

```



Local times can be converted to UTC by using `local_time` and calling `utc` on

the result:



```ruby

tz.local_time(2018, 2, 1, 7, 30, 0).utc

# => 2018-02-01 12:30:00 UTC

tz.local_time(2018, 7, 1, 8, 30, 0).utc

# => 2018-07-01 12:30:00 UTC

```



The `local_to_utc` method can also be used to convert a time object to UTC. The

offset of the time is ignored - it is treated as if it were a local time for the

time zone:



```ruby

tz.local_to_utc(Time.utc(2018, 2, 1, 7, 30, 0))

# => 2018-02-01 12:30:00 UTC

tz.local_to_utc(Time.new(2018, 2, 1, 7, 30, 0, '+01:00'))

# => 2018-02-01 12:30:00 UTC

```



Information about the time zone can be obtained from returned local times:



```ruby

local_time = tz.to_local(Time.utc(2018, 2, 1, 12, 30, 0))

local_time.utc_offset  # => -18000

local_time.dst?        # => false

local_time.zone        # => "EST"



local_time = tz.to_local(Time.utc(2018, 7, 1, 12, 30, 0))

local_time.utc_offset  # => -14400

local_time.dst?        # => true

local_time.zone        # => "EDT"

```



Time zone information can be included when formatting times with `strftime`

using the `%z` and `%Z` directives:



```ruby

tz.to_local(Time.utc(2018, 2, 1, 12, 30, 0)).strftime('%Y-%m-%d %H:%M:%S %z %Z')

# => "2018-02-01 07:30:00 -0500 EST"

tz.to_local(Time.utc(2018, 7, 1, 12, 30, 0)).strftime('%Y-%m-%d %H:%M:%S %z %Z')

# => "2018-07-01 08:30:00 -0400 EDT"

```



The `period_for` method can be used to obtain information about the observed

time zone information at a particular time as a `TZInfo::TimezonePeriod` object:



```ruby

period = tz.period_for(Time.utc(2018, 7, 1, 12, 30, 0))

period.base_utc_offset          # => -18000

period.std_offset               # => 3600

period.observed_utc_offset      # => -14400

period.abbreviation             # => "EDT"

period.dst?                     # => true

period.local_starts_at.to_time  # => 2018-03-11 03:00:00 -0400

period.local_ends_at.to_time    # => 2018-11-04 02:00:00 -0400

```



A list of transitions between periods where different rules are observed can be

obtained with the `transitions_up_to` method. The result is returned as an

`Array` of `TZInfo::TimezoneTransition` objects:



```ruby

transitions = tz.transitions_up_to(Time.utc(2019, 1, 1), Time.utc(2017, 1, 1))

transitions.map do |t|

  [t.local_end_at.to_time, t.offset.observed_utc_offset, t.offset.abbreviation]

end

# => [[2017-03-12 02:00:00 -0500, -14400, "EDT"],

#     [2017-11-05 02:00:00 -0400, -18000, "EST"],

#     [2018-03-11 02:00:00 -0500, -14400, "EDT"],

#     [2018-11-04 02:00:00 -0400, -18000, "EST"]]

```



A list of the unique offsets used by a time zone can be obtained with the

`offsets_up_to` method. The result is returned as an `Array` of

`TZInfo::TimezoneOffset` objects:



```ruby

offsets = tz.offsets_up_to(Time.utc(2019, 1, 1))

offsets.map {|o| [o.observed_utc_offset, o.abbreviation] }

# => [[-17762, "LMT"],

#     [-18000, "EST"],

#     [-14400, "EDT"],

#     [-14400, "EWT"],

#     [-14400, "EPT"]]

```



All `TZInfo::Timezone` methods that accept a time as a parameter can be used

with either instances of `Time`, `DateTime` or `TZInfo::Timestamp`. Arbitrary

`Time`-like objects that respond to both `to_i` and `subsec` and optionally

`utc_offset` will be treated as if they are instances of `Time`.



`TZInfo::Timezone` methods that both accept and return times will return an

object with a type matching that of the parameter (actually a

`TZInfo::TimeWithOffset`, `TZInfo::DateTimeWithOffset` or

`TZInfo::TimestampWithOffset` subclass when returning a local time):



```ruby

tz.to_local(Time.utc(2018, 7, 1, 12, 30, 0))

# => 2018-07-01 08:30:00 -0400

tz.to_local(DateTime.new(2018, 7, 1, 12, 30, 0))

# => #

tz.to_local(TZInfo::Timestamp.create(2018, 7, 1, 12, 30, 0, 0, :utc))

# => #

```



In addition to `local_time`, which returns `Time` instances, the

`local_datetime` and `local_timestamp` methods can be used to construct local

`DateTime` and `TZInfo::Timestamp` instances with the appropriate offset:



```ruby

tz.local_time(2018, 2, 1, 7, 30, 0)

# => 2018-02-01 07:30:00 -0500

tz.local_datetime(2018, 2, 1, 7, 30, 0)

# => #

tz.local_timestamp(2018, 2, 1, 7, 30, 0)

# => #

```



The `local_to_utc`, `local_time`, `local_datetime` and `local_timestamp` methods

may raise a `TZInfo::PeriodNotFound` or a `TZInfo::AmbiguousTime` exception.

`TZInfo::PeriodNotFound` signals that there is no equivalent UTC time (for

example, during the transition from standard time to daylight savings time when

the clocks are moved forward and an hour is skipped). `TZInfo::AmbiguousTime`

signals that there is more than one equivalent UTC time (for example, during the

transition from daylight savings time to standard time where the clocks are

moved back and an hour is repeated):



```ruby

tz.local_time(2018, 3, 11, 2, 30, 0, 0)

# raises TZInfo::PeriodNotFound (2018-03-11 02:30:00 is an invalid local time.)

tz.local_time(2018, 11, 4, 1, 30, 0, 0)

# raises TZInfo::AmbiguousTime (2018-11-04 01:30:00 is an ambiguous local time.)

```



`TZInfo::PeriodNotFound` exceptions can only be resolved by adjusting the time,

for example, by advancing an hour:



```ruby

tz.local_time(2018, 3, 11, 3, 30, 0, 0)

# => 2018-03-11 03:30:00 -0400

```



`TZInfo::AmbiguousTime` exceptions can be resolved by setting the `dst`

parameter and/or specifying a block to choose one of the interpretations:



```ruby

tz.local_time(2018, 11, 4, 1, 30, 0, 0, true)

# => 2018-11-04 01:30:00 -0400

tz.local_time(2018, 11, 4, 1, 30, 0, 0, false)

# => 2018-11-04 01:30:00 -0500



tz.local_time(2018, 11, 4, 1, 30, 0, 0) {|p| p.first }

# => 2018-11-04 01:30:00 -0400

tz.local_time(2018, 11, 4, 1, 30, 0, 0) {|p| p.last }

# => 2018-11-04 01:30:00 -0500

```



The default value of the `dst` parameter can also be set globally:



```ruby

TZInfo::Timezone.default_dst = true

tz.local_time(2018, 11, 4, 1, 30, 0, 0)

# => 2018-11-04 01:30:00 -0400

TZInfo::Timezone.default_dst = false

tz.local_time(2018, 11, 4, 1, 30, 0, 0)

# => 2018-11-04 01:30:00 -0500

```



TZInfo also provides information about

[ISO 3166-1](https://www.iso.org/iso-3166-country-codes.html) countries and

their associated time zones via the `TZInfo::Country` class.



A list of valid ISO 3166-1 (alpha-2) country codes can be obtained by calling

`TZInfo::Country.all_codes`:



```ruby

TZInfo::Country.all_codes

# => ["AD", "AE", ..., "ZW"]

```



A `TZInfo::Country` instance representing an individual time zone can be

obtained with `TZInfo::Country.get`:



```ruby

c = TZInfo::Country.get('US')

# => #

c.name

# => "United States"

```



The `zone_identifiers` method returns a list of the time zone identifiers used

in a country:



```ruby

c.zone_identifiers

# => ["America/New_York", "America/Detroit", ..., "Pacific/Honolulu"]

```



The `zone_info` method returns further information about the time zones used in

a country as an `Array` of `TZInfo::CountryTimezone` instances:



```ruby

zi = c.zone_info.first

zi.identifier               # => "America/New_York"

zi.latitude.to_f.round(5)   # => 40.71417

zi.longitude.to_f.round(5)  # => -74.00639

zi.description              # => "Eastern (most areas)"

```



The `zones` method returns an `Array` of `TZInfo::Timezone` instances for a

country. A `TZInfo::Timezone` instance can be obtained from a

`TZInfo::CountryTimezone` using the `timezone` method:



```ruby

zi.timezone.to_local(Time.utc(2018, 2, 1, 12, 30, 0))

# => 2018-02-01 07:30:00 -0500

```



For further detail, please refer to the API documentation for the

`TZInfo::Timezone` and `TZInfo::Country` classes.



## Time Zone Selection



The Time Zone Database maintainers recommend that time zone identifiers are not

made visible to end-users (see [Names of

timezones](https://data.iana.org/time-zones/theory.html#naming)).



Instead of displaying a list of time zone identifiers, time zones can be

selected by the user's country. Call `TZInfo::Country.all` to obtain a list of

`TZInfo::Country` objects, each with a unique `code` and a `name` that can be

used for display purposes.



Most countries have a single time zone. When choosing such a country, the time

zone can be inferred and selected automatically.



```ruby

croatia = TZInfo::Country.get('HR')

# => #

croatia.zone_info.length

# => 1

croatia.zone_info[0].identifier

# => "Europe/Belgrade"

```



Some countries have multiple time zones. The `zone_info` method can be used

to obtain a list of user-friendly descriptions of the available options:



```ruby

australia = TZInfo::Country.get('AU')

# => #

australia.zone_info.length

# => 13

australia.zone_info.map {|i| [i.identifier, i.description] }

# => [["Australia/Lord_Howe", "Lord Howe Island"],

#     ["Antarctica/Macquarie", "Macquarie Island"],

#     ...

#     ["Australia/Eucla", "Western Australia (Eucla)"]]

```



Please note that country information available through TZInfo is intended as an

aid to help users select a time zone data appropriate for their practical needs.

It is not intended to take or endorse any position on legal or territorial

claims.



## Compatibility



TZInfo v2.0.0 requires a minimum of Ruby MRI 1.9.3 or JRuby 1.7 (in 1.9 mode or

later).



## Thread-Safety



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.



## Documentation



API documentation for TZInfo is available on

[RubyDoc.info](https://www.rubydoc.info/gems/tzinfo/).



## License



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



## Source Code



Source code for TZInfo is available on

[GitHub](https://github.com/tzinfo/tzinfo).



## Issue Tracker



Please post any bugs, issues, feature requests or questions about TZInfo to the

[GitHub issue tracker](https://github.com/tzinfo/tzinfo/issues).



Issues with the underlying time zone data should be raised on the

[Time Zone Database Discussion mailing list](https://mm.icann.org/mailman/listinfo/tz).