in_time_zone

Returns the simultaneous time in Time.zone if a zone is given or if Time.zone_default is set. Otherwise, it returns the current time.

Time.zone = 'Hawaii'        # => 'Hawaii'
DateTime.utc(2000).in_time_zone # => Fri, 31 Dec 1999 14:00:00 HST -10:00
Date.new(2000).in_time_zone  # => Sat, 01 Jan 2000 00:00:00 HST -10:00

This method is similar to Time#localtime, except that it uses Time.zone as the local zone instead of the operating system’s time zone.

You can also pass in a TimeZone instance or string that identifies a TimeZone as an argument, and the conversion will be based on that zone instead of Time.zone.

Time.utc(2000).in_time_zone('Alaska') # => Fri, 31 Dec 1999 15:00:00 AKST -09:00
DateTime.utc(2000).in_time_zone('Alaska') # => Fri, 31 Dec 1999 15:00:00 AKST -09:00
Date.new(2000).in_time_zone('Alaska')  # => Sat, 01 Jan 2000 00:00:00 AKST -09:00