Zonebie prevents bugs in code that deals with timezones by randomly assigning a zone on every run


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Zonebie prevents bugs in code that deals with timezones by randomly assigning a zone on every run.

If Zonebie helps trigger a timezone-related bug, you can temporarily assign the ZONEBIE_TZ environment variable to make your tests deterministic while you debug (more information below).


  • MRI (2.0.x, 2.1.x, 2.2.x, 2.3.x)
  • JRuby (1.7)
  • Rubinius (2.0)

And either of these gems which adds timezone support to Ruby:

  • activesupport >= 3.0 (Rails 3.0, 3.1, 3.2, 4.0, 4.1, 4.2)
  • tzinfo >= 1.2


If using Bundler (recommended), add to Gemfile:

gem 'zonebie'

Usage with Rails & Active Support

Active Support allows setting a global timezone that will be used for many date and time calculations throughout the application.

Zonebie can set this to a random timezone at the beginning of test runs. Specifically for Active Support, it sets

Test::Unit & Minitest

Add to test/test_helper.rb:



Add to spec/spec_helper.rb:

require "zonebie/rspec"


Add a file features/support/zonebie.rb with the following contents:


Usage with TZInfo

Zonebie can use the tzinfo gem, allowing it to work outside of Active Support (Rails).

However, Zonebie.set_random_timezone does not work outside of Active Support because there is not a concept of a global timezone setting. If you simply need a random timezone for some other part of your tests, Zonebie can help.

zone = TZInfo::Timezone.get(Zonebie.random_timezone)

# Also works in Rails/Active Support
zone = ActiveSupport::TimeZone[Zonebie.random_timezone]

Reproducing Bugs

When Zonebie.set_random_timezone is called, Zonebie assigns a timezone and prints a message to STDOUT:

[Zonebie] Setting timezone: ZONEBIE_TZ="Eastern Time (US & Canada)"

If you would rather that Zonebie not print out this information during your tests, put Zonebie in quiet mode before calling set_random_timezone:

Zonebie.quiet = true

To rerun tests with a specific timezone (e.g., to reproduce a bug that only seems present in one zone), set the ZONEBIE_TZ environment variable:

# Assuming tests run with simply `rake`
ZONEBIE_TZ="Eastern Time (US & Canada)" rake


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request