How to Work With Time Zones in Rails

When dealing with time zones in Rails, there is one key fact to keep in mind:

Rails has configurable time zones, while
Ruby is always in the server's time zone

Thus, using Ruby's time API will give you wrong results for different time zones.

"Without" time zones

You can not actually disable time zones, because their existence is a fact. You can, however, tell Rails the only single time zone you'll need is the server's.

Copyconfig.time_zone = "Berlin" # Local time zone
config.active_record.default_timezone = :local
config.active_record.time_zone_aware_attributes = false    

Now you may again use both Ruby's and Rails' whole time API.

With different time zones

For consistency, you should only use Rails' methods, but the hard thing is to know which method originates from Ruby and which from Rails. To simplify this, adhere to the following suggestion:

Use Time.zone for everything time-related

Copy# Examples of Time.zone
Time.zone.now # instead of Time.now, DateTime.now
Time.zone.today # instead of Date.today
Time.zone.local(...) # instead of Date.new, DateTime.new
Time.zone.at(...) # instead of Time.at
Time.zone.parse(...) # instead of Time.parse

date.beginning_of_day # instead of date.to_time

Things like 2.hours.ago work as expected, because they're provided by Rails. Still, prefer using Time.zone.now + 2.hours as it will leave no doubt about time zones being respected.

In case you should get time objects without time zone information, you can still turn them into zoned times by calling #in_time_zone, e.g.: Time.now.in_time_zone.

Reference

• The Exhaustive Guide to Rails Time Zones Show archive.org snapshot - a quick introduction to how and why things can go wrong when you're using time zones
• Working with or without time zones in Rails applications