Refactored common date and time calculations.

* Added the `DateAndTime::Calculations` module that is included in Time
  and Date. It houses common calculations to reduce duplicated code.
* Simplified and cleaned-up the calculation code.
* Removed duplication in tests by adding a behavior module for shared
  tests. I also added some missing tests.

3 files changed, 218 insertions, 379 deletions

diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 7fe4161fb4..ef2c98c2ae 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -3,17 +3,10 @@ require 'active_support/duration'
 require 'active_support/core_ext/object/acts_like'
 require 'active_support/core_ext/date/zones'
 require 'active_support/core_ext/time/zones'
+require 'active_support/core_ext/date_and_time/calculations'
 
 class Date
-  DAYS_INTO_WEEK = {
-    :monday => 0,
-    :tuesday => 1,
-    :wednesday => 2,
-    :thursday => 3,
-    :friday => 4,
-    :saturday => 5,
-    :sunday => 6
-  }
+  include DateAndTime::Calculations
 
   class << self
     # Returns a new Date representing the date 1 day ago (i.e. yesterday's date).
@@ -32,21 +25,6 @@ class Date
     end
   end
 
-  # Returns true if the Date object's date lies in the past. Otherwise returns false.
-  def past?
-    self < ::Date.current
-  end
-
-  # Returns true if the Date object's date is today.
-  def today?
-    to_date == ::Date.current # we need the to_date because of DateTime
-  end
-
-  # Returns true if the Date object's date lies in the future.
-  def future?
-    self > ::Date.current
-  end
-
   # Converts Date to a Time (or DateTime if necessary) with the time portion set to the beginning of the day (0:00)
   # and then subtracts the specified number of seconds.
   def ago(seconds)
@@ -116,161 +94,4 @@ class Date
       options.fetch(:day, day)
     )
   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)
-  end
-
-  # Returns a new Date/DateTime representing the time a number of specified months in the future.
-  def months_since(months)
-    advance(:months => months)
-  end
-
-  # Returns a new Date/DateTime representing the time a number of specified years ago.
-  def years_ago(years)
-    advance(:years => -years)
-  end
-
-  # Returns a new Date/DateTime representing the time a number of specified years in the future.
-  def years_since(years)
-    advance(:years => years)
-  end
-
-  # Returns number of days to start of this week. Week is assumed to start on
-  # +start_day+, default is +:monday+.
-  def days_to_week_start(start_day = :monday)
-    start_day_number = DAYS_INTO_WEEK[start_day]
-    current_day_number = wday != 0 ? wday - 1 : 6
-    (current_day_number - start_day_number) % 7
-  end
-
-  # Returns a new +Date+/+DateTime+ representing the start of this week. Week is
-  # assumed to start on +start_day+, default is +:monday+. +DateTime+ objects
-  # have their time set to 0:00.
-  def beginning_of_week(start_day = :monday)
-    days_to_start = days_to_week_start(start_day)
-    result = self - days_to_start
-    acts_like?(:time) ? result.midnight : result
-  end
-  alias :at_beginning_of_week :beginning_of_week
-
-  # Returns a new +Date+/+DateTime+ representing the start of this week. Week is
-  # assumed to start on a Monday. +DateTime+ objects have their time set to 0:00.
-  def monday
-    beginning_of_week
-  end
-
-  # Returns a new +Date+/+DateTime+ representing the end of this week. Week is
-  # assumed to start on +start_day+, default is +:monday+. +DateTime+ objects
-  # have their time set to 23:59:59.
-  def end_of_week(start_day = :monday)
-    days_to_end = 6 - days_to_week_start(start_day)
-    result = self + days_to_end.days
-    acts_like?(:time) ? result.end_of_day : result
-  end
-  alias :at_end_of_week :end_of_week
-
-  # Returns a new +Date+/+DateTime+ representing the end of this week. Week is
-  # assumed to start on a Monday. +DateTime+ objects have their time set to 23:59:59.
-  def sunday
-    end_of_week
-  end
-
-  # Returns a new +Date+/+DateTime+ representing the given +day+ in the previous
-  # week. Default is +:monday+. +DateTime+ objects have their time set to 0:00.
-  def prev_week(day = :monday)
-    result = (self - 7).beginning_of_week + DAYS_INTO_WEEK[day]
-    acts_like?(:time) ? result.change(:hour => 0) : result
-  end
-  alias :last_week :prev_week
-
-  # Alias of prev_month
-  alias :last_month :prev_month
-
-  # Alias of prev_year
-  alias :last_year :prev_year
-
-  # Returns a new Date/DateTime representing the start of the given day in next week (default is :monday).
-  def next_week(day = :monday)
-    result = (self + 7).beginning_of_week + DAYS_INTO_WEEK[day]
-    acts_like?(:time) ? result.change(:hour => 0) : result
-  end
-
-  # Short-hand for months_ago(3)
-  def prev_quarter
-    months_ago(3)
-  end
-  alias_method :last_quarter, :prev_quarter
-
-  # Short-hand for months_since(3)
-  def next_quarter
-    months_since(3)
-  end
-
-  # Returns a new Date/DateTime representing the start of the month (1st of the month; DateTime objects will have time set to 0:00)
-  def beginning_of_month
-    acts_like?(:time) ? change(:day => 1, :hour => 0) : change(:day => 1)
-  end
-  alias :at_beginning_of_month :beginning_of_month
-
-  # Returns a new Date/DateTime representing the end of the month (last day of the month; DateTime objects will have time set to 0:00)
-  def end_of_month
-    last_day = ::Time.days_in_month(month, year)
-    if acts_like?(:time)
-      change(:day => last_day, :hour => 23, :min => 59, :sec => 59)
-    else
-      change(:day => last_day)
-    end
-  end
-  alias :at_end_of_month :end_of_month
-
-  # Returns a new Date/DateTime representing the start of the quarter (1st of january, april, july, october; DateTime objects will have time set to 0:00)
-  def beginning_of_quarter
-    first_quarter_month = [10, 7, 4, 1].detect { |m| m <= month }
-    beginning_of_month.change(:month => first_quarter_month)
-  end
-  alias :at_beginning_of_quarter :beginning_of_quarter
-
-  # Returns a new Date/DateTime representing the end of the quarter (last day of march, june, september, december; DateTime objects will have time set to 23:59:59)
-  def end_of_quarter
-    last_quarter_month = [3, 6, 9, 12].detect { |m| m >= month }
-    beginning_of_month.change(:month => last_quarter_month).end_of_month
-  end
-  alias :at_end_of_quarter :end_of_quarter
-
-  # Returns a new Date/DateTime representing the start of the year (1st of january; DateTime objects will have time set to 0:00)
-  def beginning_of_year
-    if acts_like?(:time)
-      change(:month => 1, :day => 1, :hour => 0)
-    else
-      change(:month => 1, :day => 1)
-    end
-  end
-  alias :at_beginning_of_year :beginning_of_year
-
-  # Returns a new Time representing the end of the year (31st of december; DateTime objects will have time set to 23:59:59)
-  def end_of_year
-    if acts_like?(:time)
-      change(:month => 12, :day => 31, :hour => 23, :min => 59, :sec => 59)
-    else
-      change(:month => 12, :day => 31)
-    end
-  end
-  alias :at_end_of_year :end_of_year
-
-  # Convenience method which returns a new Date/DateTime representing the time 1 day ago
-  def yesterday
-    self - 1
-  end
-
-  # Convenience method which returns a new Date/DateTime representing the time 1 day since the instance time
-  def tomorrow
-    self + 1
-  end
 end
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
new file mode 100644
index 0000000000..56c1b06608
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -0,0 +1,213 @@
+module DateAndTime
+  module Calculations
+    DAYS_INTO_WEEK = {
+      :monday    => 0,
+      :tuesday   => 1,
+      :wednesday => 2,
+      :thursday  => 3,
+      :friday    => 4,
+      :saturday  => 5,
+      :sunday    => 6
+    }
+
+    # Returns a new date/time representing yesterday.
+    def yesterday
+      advance(:days => -1)
+    end
+
+    # Returns a new date/time representing tomorrow.
+    def tomorrow
+      advance(:days => 1)
+    end
+
+    # Returns true if the date/time is today.
+    def today?
+      to_date == ::Date.current
+    end
+
+    # Returns true if the date/time is in the past.
+    def past?
+      self < self.class.current
+    end
+
+    # Returns true if the date/time is in the future.
+    def future?
+      self > self.class.current
+    end
+
+    # Returns a new date/time the specified number of days ago.
+    def days_ago(days)
+      advance(:days => -days)
+    end
+
+    # Returns a new date/time the specified number of days in the future.
+    def days_since(days)
+      advance(:days => days)
+    end
+
+    # Returns a new date/time the specified number of weeks ago.
+    def weeks_ago(weeks)
+      advance(:weeks => -weeks)
+    end
+
+    # Returns a new date/time the specified number of weeks in the future.
+    def weeks_since(weeks)
+      advance(:weeks => weeks)
+    end
+
+    # Returns a new date/time the specified number of months ago.
+    def months_ago(months)
+      advance(:months => -months)
+    end
+
+    # Returns a new date/time the specified number of months in the future.
+    def months_since(months)
+      advance(:months => months)
+    end
+
+    # Returns a new date/time the specified number of years ago.
+    def years_ago(years)
+      advance(:years => -years)
+    end
+
+    # Returns a new date/time the specified number of years in the future.
+    def years_since(years)
+      advance(:years => years)
+    end
+
+    # 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) }
+    end
+    alias :at_beginning_of_month :beginning_of_month
+
+    # Returns a new date/time at the start of the quarter.
+    # Example: 1st January, 1st July, 1st October.
+    # DateTime objects will have a time set to 0:00.
+    def beginning_of_quarter
+      first_quarter_month = [10, 7, 4, 1].detect { |m| m <= month }
+      beginning_of_month.change(:month => first_quarter_month)
+    end
+    alias :at_beginning_of_quarter :beginning_of_quarter
+
+    # Returns a new date/time at the end of the quarter.
+    # Example: 31st March, 30th June, 30th September.
+    # DateTIme objects will have a time set to 23:59:59.
+    def end_of_quarter
+      last_quarter_month = [3, 6, 9, 12].detect { |m| m >= month }
+      beginning_of_month.change(:month => last_quarter_month).end_of_month
+    end
+    alias :at_end_of_quarter :end_of_quarter
+
+    # Return a new date/time at the beginning of the year.
+    # Example: 1st January.
+    # DateTime objects will have a time set to 0:00.
+    def beginning_of_year
+      change(:month => 1).beginning_of_month
+    end
+    alias :at_beginning_of_year :beginning_of_year
+
+    # Returns a new date/time representing the given day in the next week.
+    # Default is :monday.
+    # DateTime objects have their time set to 0:00.
+    def next_week(day = :monday)
+      first_hour{ weeks_since(1).beginning_of_week.days_since(DAYS_INTO_WEEK[day]) }
+    end
+
+    # Short-hand for months_since(1).
+    def next_month
+      months_since(1)
+    end
+
+    # Short-hand for months_since(3)
+    def next_quarter
+      months_since(3)
+    end
+
+    # Short-hand for years_since(1).
+    def next_year
+      years_since(1)
+    end
+
+    # Returns a new date/time representing the given day in the previous week.
+    # Default is :monday.
+    # DateTime objects have their time set to 0:00.
+    def prev_week(day = :monday)
+      first_hour{ weeks_ago(1).beginning_of_week.days_since(DAYS_INTO_WEEK[day]) }
+    end
+    alias_method :last_week, :prev_week
+
+    # Short-hand for months_ago(1).
+    def prev_month
+      months_ago(1)
+    end
+    alias_method :last_month, :prev_month
+
+    # Short-hand for months_ago(3).
+    def prev_quarter
+      months_ago(3)
+    end
+    alias_method :last_quarter, :prev_quarter
+
+    # Short-hand for years_ago(1).
+    def prev_year
+      years_ago(1)
+    end
+    alias_method :last_year, :prev_year
+
+    # Returns the number of days to the start of the week on the given day.
+    # Default is :monday.
+    def days_to_week_start(start_day = :monday)
+      start_day_number = DAYS_INTO_WEEK[start_day]
+      current_day_number = wday != 0 ? wday - 1 : 6
+      (current_day_number - start_day_number) % 7
+    end
+
+    # Returns a new date/time representing the start of this week on the given day.
+    # Default is :monday.
+    # DateTime objects have their time set to 0:00.
+    def beginning_of_week(start_day = :monday)
+      result = days_ago(days_to_week_start(start_day))
+      acts_like?(:time) ? result.midnight : result
+    end
+    alias :at_beginning_of_week :beginning_of_week
+    alias :monday :beginning_of_week
+
+    # Returns a new date/time representing the end of this week on the given day.
+    # Default is :monday (i.e end of Sunday).
+    # DateTime objects have their time set to 23:59:59.
+    def end_of_week(start_day = :monday)
+      last_hour{ days_since(6 - days_to_week_start(start_day)) }
+    end
+    alias :at_end_of_week :end_of_week
+    alias :sunday :end_of_week
+
+    # Returns a new date/time representing the end of the month.
+    # 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) }
+    end
+    alias :at_end_of_month :end_of_month
+
+    # Returns a new date/time representing the end of the year.
+    # DateTime objects will have a time set to 23:59:59.
+    def end_of_year
+      result = change(:month => 12).end_of_month
+    end
+    alias :at_end_of_year :end_of_year
+
+    private
+
+    def first_hour
+      result = yield
+      acts_like?(:time) ? result.change(:hour => 0) : result
+    end
+
+    def last_hour
+      result = yield
+      acts_like?(:time) ? result.end_of_day : result
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index d0f574f2ba..fd43849504 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -2,18 +2,12 @@ require 'active_support/duration'
 require 'active_support/core_ext/time/conversions'
 require 'active_support/time_with_zone'
 require 'active_support/core_ext/time/zones'
+require 'active_support/core_ext/date_and_time/calculations'
 
 class Time
+  include DateAndTime::Calculations
+
   COMMON_YEAR_DAYS_IN_MONTH = [nil, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
-  DAYS_INTO_WEEK = {
-    :monday    => 0,
-    :tuesday   => 1,
-    :wednesday => 2,
-    :thursday  => 3,
-    :friday    => 4,
-    :saturday  => 5,
-    :sunday    => 6
-  }
 
   class << self
     # Overriding case equality method so that it returns true for ActiveSupport::TimeWithZone instances
@@ -63,21 +57,6 @@ class Time
     end
   end
 
-  # Tells whether the Time object's time lies in the past
-  def past?
-    self < ::Time.current
-  end
-
-  # Tells whether the Time object's time is today
-  def today?
-    to_date == ::Date.current
-  end
-
-  # Tells whether the Time object's time lies in the future
-  def future?
-    self > ::Time.current
-  end
-
   # Seconds since midnight: Time.now.seconds_since_midnight
   def seconds_since_midnight
     to_i - change(:hour => 0).to_i + (usec / 1.0e+6)
@@ -146,116 +125,6 @@ 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)
-  end
-
-  # Returns a new Time representing the time a number of specified months in the future
-  def months_since(months)
-    advance(:months => months)
-  end
-
-  # Returns a new Time representing the time a number of specified years ago
-  def years_ago(years)
-    advance(:years => -years)
-  end
-
-  # Returns a new Time representing the time a number of specified years in the future
-  def years_since(years)
-    advance(:years => years)
-  end
-
-  # Short-hand for years_ago(1)
-  def prev_year
-    years_ago(1)
-  end
-  alias_method :last_year, :prev_year
-
-  # Short-hand for years_since(1)
-  def next_year
-    years_since(1)
-  end
-
-  # Short-hand for months_ago(1)
-  def prev_month
-    months_ago(1)
-  end
-  alias_method :last_month, :prev_month
-
-  # Short-hand for months_since(1)
-  def next_month
-    months_since(1)
-  end
-
-  # Short-hand for months_ago(3)
-  def prev_quarter
-    months_ago(3)
-  end
-  alias_method :last_quarter, :prev_quarter
-
-  # Short-hand for months_since(3)
-  def next_quarter
-    months_since(3)
-  end
-
-  # Returns number of days to start of this week, week starts on start_day (default is :monday).
-  def days_to_week_start(start_day = :monday)
-    start_day_number = DAYS_INTO_WEEK[start_day]
-    current_day_number = wday != 0 ? wday - 1 : 6
-    days_span = current_day_number - start_day_number
-
-    days_span >= 0 ? days_span : 7 + days_span
-  end
-
-  # Returns a new Time representing the "start" of this week, week starts on start_day (default is :monday, i.e. Monday, 0:00).
-  def beginning_of_week(start_day = :monday)
-    days_to_start = days_to_week_start(start_day)
-    (self - days_to_start.days).midnight
-  end
-  alias :at_beginning_of_week :beginning_of_week
-
-  # Returns a new +Date+/+DateTime+ representing the start of this week. Week is
-  # assumed to start on a Monday. +DateTime+ objects have their time set to 0:00.
-  def monday
-    beginning_of_week
-  end
-
-  # Returns a new Time representing the end of this week, week starts on start_day (default is :monday, i.e. end of Sunday).
-  def end_of_week(start_day = :monday)
-    days_to_end =  6 - days_to_week_start(start_day)
-    (self + days_to_end.days).end_of_day
-  end
-  alias :at_end_of_week :end_of_week
-
-  # Returns a new +Date+/+DateTime+ representing the end of this week. Week is
-  # assumed to start on a Monday. +DateTime+ objects have their time set to 23:59:59.
-  def sunday
-    end_of_week
-  end
-
-  # 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
-  alias_method :last_week, :prev_week
-
-  # 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)
-  end
-
   # Returns a new Time representing the start of the day (0:00)
   def beginning_of_day
     #(self - seconds_since_midnight).change(:usec => 0)
@@ -290,70 +159,6 @@ class Time
     )
   end
 
-  # Returns a new Time representing the start of the month (1st of the month, 0:00)
-  def beginning_of_month
-    #self - ((self.mday-1).days + self.seconds_since_midnight)
-    change(:day => 1, :hour => 0)
-  end
-  alias :at_beginning_of_month :beginning_of_month
-
-  # Returns a new Time representing the end of the month (end of the last day of the month)
-  def end_of_month
-    #self - ((self.mday-1).days + self.seconds_since_midnight)
-    last_day = ::Time.days_in_month(month, year)
-    change(
-      :day  => last_day,
-      :hour => 23,
-      :min  => 59,
-      :sec  => 59,
-      :usec => Rational(999999999, 1000)
-    )
-  end
-  alias :at_end_of_month :end_of_month
-
-  # Returns  a new Time representing the start of the quarter (1st of january, april, july, october, 0:00)
-  def beginning_of_quarter
-    first_quarter_month = [10, 7, 4, 1].detect { |m| m <= month }
-    beginning_of_month.change(:month => first_quarter_month)
-  end
-  alias :at_beginning_of_quarter :beginning_of_quarter
-
-  # Returns a new Time representing the end of the quarter (end of the last day of march, june, september, december)
-  def end_of_quarter
-    last_quarter_month = [3, 6, 9, 12].detect { |m| m >= month }
-    beginning_of_month.change(:month => last_quarter_month).end_of_month
-  end
-  alias :at_end_of_quarter :end_of_quarter
-
-  # Returns a new Time representing the start of the year (1st of january, 0:00)
-  def beginning_of_year
-    change(:month => 1, :day => 1, :hour => 0)
-  end
-  alias :at_beginning_of_year :beginning_of_year
-
-  # Returns a new Time representing the end of the year (end of the 31st of december)
-  def end_of_year
-    change(
-      :month => 12,
-      :day   => 31,
-      :hour  => 23,
-      :min   => 59,
-      :sec   => 59,
-      :usec  => Rational(999999999, 1000)
-    )
-  end
-  alias :at_end_of_year :end_of_year
-
-  # Convenience method which returns a new Time representing the time 1 day ago
-  def yesterday
-    advance(:days => -1)
-  end
-
-  # Convenience method which returns a new Time representing the time 1 day since the instance time
-  def tomorrow
-    advance(:days => 1)
-  end
-
   # Returns a Range representing the whole day of the current time.
   def all_day
     beginning_of_day..end_of_day