1 files changed, 36 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index b0dd6b7e8c..ecb9fb6785 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -330,6 +330,42 @@ module ActiveSupport
       since(-other)
     end
 
+    # Returns a new +ActiveSupport::TimeWithZone+ where one or more of the elements have
+    # been changed according to the +options+ parameter. The time options (<tt>:hour</tt>,
+    # <tt>:min</tt>, <tt>:sec</tt>, <tt>:usec</tt>, <tt>:nsec</tt>) reset cascadingly,
+    # so if only the hour is passed, then minute, sec, usec and nsec is set to 0. If the
+    # hour and minute is passed, then sec, usec and nsec is set to 0. The +options+
+    # parameter takes a hash with any of these keys: <tt>:year</tt>, <tt>:month</tt>,
+    # <tt>:day</tt>, <tt>:hour</tt>, <tt>:min</tt>, <tt>:sec</tt>, <tt>:usec</tt>,
+    # <tt>:nsec</tt>, <tt>:offset</tt>, <tt>:zone</tt>. Pass either <tt>:usec</tt>
+    # or <tt>:nsec</tt>, not both. Similarly, pass either <tt>:zone</tt> or
+    # <tt>:offset</tt>, not both.
+    #
+    #   t = Time.zone.now          # => Fri, 14 Apr 2017 11:45:15 EST -05:00
+    #   t.change(year: 2020)       # => Tue, 14 Apr 2020 11:45:15 EST -05:00
+    #   t.change(hour: 12)         # => Fri, 14 Apr 2017 12:00:00 EST -05:00
+    #   t.change(min: 30)          # => Fri, 14 Apr 2017 11:30:00 EST -05:00
+    #   t.change(offset: "-10:00") # => Fri, 14 Apr 2017 11:45:15 HST -10:00
+    #   t.change(zone: "Hawaii")   # => Fri, 14 Apr 2017 11:45:15 HST -10:00
+    def change(options)
+      if options[:zone] && options[:offset]
+        raise ArgumentError, "Can't change both :offset and :zone at the same time: #{options.inspect}"
+      end
+
+      new_time = time.change(options)
+
+      if options[:zone]
+        new_zone = ::Time.find_zone(options[:zone])
+      elsif options[:offset]
+        new_zone = ::Time.find_zone(new_time.utc_offset)
+      end
+
+      new_zone ||= time_zone
+      periods = new_zone.periods_for_local(new_time)
+
+      self.class.new(nil, new_zone, new_time, periods.include?(period) ? period : nil)
+    end
+
     # Uses Date to provide precise Time calculations for years, months, and days
     # according to the proleptic Gregorian calendar. The result is returned as a
     # new TimeWithZone object.