2 files changed, 25 insertions, 3 deletions
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 1856b4dd8b..f34185f22c 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -5,6 +5,8 @@ require 'active_support/core_ext/date/zones'
 require 'active_support/core_ext/time/zones'
 
 class Date
+  DAYS_INTO_WEEK = { :monday => 0, :tuesday => 1, :wednesday => 2, :thursday => 3, :friday => 4, :saturday => 5, :sunday => 6 }
+
   if RUBY_VERSION < '1.9'
     undef :>>
 
@@ -127,6 +129,11 @@ class Date
     )
   end
 
+  # Returns a new Date/DateTime representing the time a number of specified weeks ago.
+  def weeks_ago(weeks)
+    advance(:weeks => -weeks)
+  end
+
   # Returns a new Date/DateTime representing the time a number of specified months ago.
   def months_ago(months)
     advance(:months => -months)
@@ -185,10 +192,15 @@ class Date
   alias :sunday :end_of_week
   alias :at_end_of_week :end_of_week
 
+  # Returns a new Date/DateTime representing the start of the given day in the previous week (default is Monday).
+  def prev_week(day = :monday)
+    result = (self - 7).beginning_of_week + DAYS_INTO_WEEK[day]
+    self.acts_like?(:time) ? result.change(:hour => 0) : result
+  end
+
   # Returns a new Date/DateTime representing the start of the given day in next week (default is Monday).
   def next_week(day = :monday)
-    days_into_week = { :monday => 0, :tuesday => 1, :wednesday => 2, :thursday => 3, :friday => 4, :saturday => 5, :sunday => 6}
-    result = (self + 7).beginning_of_week + days_into_week[day]
+    result = (self + 7).beginning_of_week + DAYS_INTO_WEEK[day]
     self.acts_like?(:time) ? result.change(:hour => 0) : result
   end
 
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index d430751623..fa052fa86b 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -22,7 +22,7 @@ class Time
 
     # Returns a new Time if requested year can be accommodated by Ruby's Time class
     # (i.e., if year is within either 1970..2038 or 1902..2038, depending on system architecture);
-    # otherwise returns a DateTime
+    # otherwise returns a DateTime.
     def time_with_datetime_fallback(utc_or_local, year, month=1, day=1, hour=0, min=0, sec=0, usec=0)
       time = ::Time.send(utc_or_local, year, month, day, hour, min, sec, usec)
       # This check is needed because Time.utc(y) returns a time object in the 2000s for 0 <= y <= 138.
@@ -117,6 +117,11 @@ class Time
   end
   alias :in :since
 
+  # Returns a new Time representing the time a number of specified weeks ago.
+  def weeks_ago(weeks)
+    advance(:weeks => -weeks)
+  end
+
   # Returns a new Time representing the time a number of specified months ago
   def months_ago(months)
     advance(:months => -months)
@@ -172,6 +177,11 @@ class Time
   end
   alias :at_end_of_week :end_of_week
 
+  # Returns a new Time representing the start of the given day in the previous week (default is Monday).
+  def prev_week(day = :monday)
+    ago(1.week).beginning_of_week.since(DAYS_INTO_WEEK[day].day).change(:hour => 0)
+  end
+
   # Returns a new Time representing the start of the given day in next week (default is Monday).
   def next_week(day = :monday)
     since(1.week).beginning_of_week.since(DAYS_INTO_WEEK[day].day).change(:hour => 0)