2 files changed, 50 insertions, 11 deletions
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index 0d14cba7cc..c869a0e210 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -78,7 +78,7 @@ module DateAndTime
     # Returns a new date/time at the start of the month.
     # DateTime objects will have a time set to 0:00.
     def beginning_of_month
-      first_hour{ change(:day => 1) }
+      first_hour(change(:day => 1))
     end
     alias :at_beginning_of_month :beginning_of_month
 
@@ -113,7 +113,7 @@ module DateAndTime
     # which is determined by +Date.beginning_of_week+ or +config.beginning_of_week+
     # when set. +DateTime+ objects have their time set to 0:00.
     def next_week(given_day_in_next_week = Date.beginning_of_week)
-      first_hour{ weeks_since(1).beginning_of_week.days_since(days_span(given_day_in_next_week)) }
+      first_hour(weeks_since(1).beginning_of_week.days_since(days_span(given_day_in_next_week)))
     end
 
     # Short-hand for months_since(1).
@@ -136,7 +136,7 @@ module DateAndTime
     # +Date.beginning_of_week+ or +config.beginning_of_week+ when set.
     # DateTime objects have their time set to 0:00.
     def prev_week(start_day = Date.beginning_of_week)
-      first_hour{ weeks_ago(1).beginning_of_week.days_since(days_span(start_day)) }
+      first_hour(weeks_ago(1).beginning_of_week.days_since(days_span(start_day)))
     end
     alias_method :last_week, :prev_week
 
@@ -188,7 +188,7 @@ module DateAndTime
     # +Date.beginning_of_week+ or +config.beginning_of_week+ when set.
     # DateTime objects have their time set to 23:59:59.
     def end_of_week(start_day = Date.beginning_of_week)
-      last_hour{ days_since(6 - days_to_week_start(start_day)) }
+      last_hour(days_since(6 - days_to_week_start(start_day)))
     end
     alias :at_end_of_week :end_of_week
 
@@ -202,7 +202,7 @@ module DateAndTime
     # DateTime objects will have a time set to 23:59:59.
     def end_of_month
       last_day = ::Time.days_in_month(month, year)
-      last_hour{ days_since(last_day - day) }
+      last_hour(days_since(last_day - day))
     end
     alias :at_end_of_month :end_of_month
 
@@ -215,14 +215,12 @@ module DateAndTime
 
     private
 
-    def first_hour
-      result = yield
-      acts_like?(:time) ? result.change(:hour => 0) : result
+    def first_hour(date_or_time)
+      date_or_time.acts_like?(:time) ? date_or_time.beginning_of_day : date_or_time
     end
 
-    def last_hour
-      result = yield
-      acts_like?(:time) ? result.end_of_day : result
+    def last_hour(date_or_time)
+      date_or_time.acts_like?(:time) ? date_or_time.end_of_day : date_or_time
     end
 
     def days_span(day)
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/zones.rb b/activesupport/lib/active_support/core_ext/date_and_time/zones.rb
new file mode 100644
index 0000000000..96c6df9407
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/date_and_time/zones.rb
@@ -0,0 +1,41 @@
+module DateAndTime
+  module Zones
+    # Returns the simultaneous time in <tt>Time.zone</tt> 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 <tt>Time.zone</tt> 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 <tt>Time.zone</tt>.
+    #
+    #   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
+    def in_time_zone(zone = ::Time.zone)
+      time_zone = ::Time.find_zone! zone
+      time = acts_like?(:time) ? self : nil
+
+      if time_zone
+        time_with_zone(time, time_zone)
+      else
+        time || self.to_time
+      end
+    end
+
+    private
+
+    def time_with_zone(time, zone)
+      if time
+        ActiveSupport::TimeWithZone.new(time.utc? ? time : time.getutc, zone)
+      else
+        ActiveSupport::TimeWithZone.new(nil, zone, to_time(:utc))
+      end
+    end
+  end
+end
+