TimeZone

Crystal already has own logic of taking care of time zones. Therefore prefer native crystal implementation over this library.

Time Zone provides daylight savings aware transformations between times in different time zones. Also this is a port of ruby tzinfo gem.

Installation

Add this to your application's shard.yml:

dependencies:
  time_zone:
    github: imdrasil/time_zone

Usage

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 "time_zone"

tz = TimeZone::Zone.get("America/New_York")
local = tz.utc_to_local(Time.utc(2005,8,29,15,35,0))

Note that the local Time returned will be kind of UTC (local.kind will return Time::Kind::Utc). This is because the Crystal Time class only supports two timezones:

• UTC
• 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 time zone information of the local Time object is ignored (TimeZone 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.new(2006,6,26,1,0,0))
tz.local_to_utc(Time.utc(2006,6,26,1,0,0))

The current local time in a Zone can be obtained with the TimeZone::Zone#now method:

now = tz.now

A list of all the available timezone identifiers can be obtained using the TimeZone::Zone.all_identifiers method. TimeZone::Zone.all can be called to get an Array of all the TimeZone::Zone and TimeZone::LinkedZone instances.

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

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

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

TimeZone::Time

To hold time zone in the time object TimeZone::Time struct could be used. It provides almost same interface as the Time does. Also there is 2 methods added to Time:

• #to_time_zone_time - converts current time object to TimeZone::Time in default time zone;
• ::zone - returns default time zone.

To set or get default time zone next code can be used:

TimeZone::Zone.default # tries to read time zone from `TZ`
                       # environment variable, otherwise UTC
                       # will be used
TimeZone::Zone.default = "America/New_York"
# or
TimeZone::Zone.default = TimeZone::Zone.get("America/New_York")

To create specific date in time zone:

zone.new(2010, 10, 19)
Time.zone.new(2012, 12, 12) # in the default time zone

Also TimeZone::Time could be parsed from string with grepping given time zone offset:

# Time zone will be set to Etc/GMT-5
TimeZone::Time.parse("2014-10-31 10:11:12 +05:00", "%F %T %z")

Development

Data Generating

All code in src/time_zone/data folder is automatically generated so please don't try to make any change there because they will be lost after next regenerating. To generate new version please paste all files from original repo to the data folder in this repo root and invoke ruby scripts/build.rb.

Contributing

1. Fork it ( https://github.com/imdrasil/time_zone/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• imdrasil Roman Kalnytskyi - creator, maintainer