From 8ce8b4973c473de3215cfe07e2b5e4f80f0379aa Mon Sep 17 00:00:00 2001
From: Dan Barry <dan@bakineggs.com>
Date: Sun, 12 Oct 2008 20:36:26 -0500
Subject: [PATCH] Date.durations_between: Date.days_between, Date.weeks_between, Date.months_between, Date.years_between

---
 .../active_support/core_ext/date/calculations.rb   |   25 +++++++++++
 activesupport/test/core_ext/date_ext_test.rb       |   44 ++++++++++++++++++++
 2 files changed, 69 insertions(+), 0 deletions(-)

diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 43d70c7..d188405 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -30,6 +30,31 @@ module ActiveSupport #:nodoc:
           def current
             ::Time.zone_default ? ::Time.zone.today : ::Date.today
           end
+
+          def durations_between(start, finish, duration)
+            return durations_between(finish, start, duration) if start > finish
+            count = 0
+            while ((start += duration) <= finish)
+              count += 1
+            end
+            count + ((finish - (start - duration)) / (finish + duration - finish))
+          end
+
+          def days_between(start, finish)
+            durations_between(start, finish, 1.day)
+          end
+
+          def weeks_between(start, finish)
+            durations_between(start, finish, 1.week)
+          end
+
+          def months_between(start, finish)
+            durations_between(start, finish, 1.month)
+          end
+
+          def years_between(start, finish)
+            durations_between(start, finish, 1.year)
+          end
         end
 
         # Tells whether the Date object's date lies in the past
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index b53c754..a5fad46 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -256,6 +256,50 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     end
   end
 
+  def test_durations_between
+    assert_equal 2, Date.durations_between(Date.new(1999, 12, 29), Date.new(1999, 12, 31), 1.day)
+  end
+
+  def test_durations_between_wrapping
+    assert_equal 1, Date.durations_between(Date.new(1999, 12, 31), Date.new(2000, 1, 1), 1.day)
+  end
+
+  def test_durations_between_fractions
+    assert_equal 1.25, Date.durations_between(Date.new(1999, 12, 25), Date.new(1999, 12, 30), 4.days)
+  end
+
+  def test_days_between
+    assert_equal 2, Date.days_between(Date.new(1999, 12, 29), Date.new(1999, 12, 31))
+  end
+
+  def test_days_between_wrapping
+    assert_equal 3, Date.days_between(Date.new(1999, 12, 30), Date.new(2000, 1, 2))
+  end
+
+  def test_weeks_between
+    assert_equal 2, Date.weeks_between(Date.new(1999, 12, 5), Date.new(1999, 12, 19))
+  end
+
+  def test_months_between
+    assert_equal 2, Date.months_between(Date.new(1999, 10, 1), Date.new(1999, 12, 1))
+  end
+
+  def test_months_between_wrapping
+    assert_equal 4, Date.months_between(Date.new(1999, 10, 1), Date.new(2000, 2, 1))
+  end
+
+  def test_months_between_fractions
+    assert_equal 1.5, Date.months_between(Date.new(1999, 10, 15), Date.new(1999, 11, 30))
+  end
+
+  def test_years_between
+    assert_equal 2, Date.years_between(Date.new(1999, 12, 31), Date.new(2001, 12, 31))
+  end
+
+  def test_years_between_fractions
+    assert_equal 1.2, Date.years_between(Date.new(1999, 6, 1), Date.new(2000, 8, 13))
+  end
+
   protected
     def with_env_tz(new_tz = 'US/Eastern')
       old_tz, ENV['TZ'] = ENV['TZ'], new_tz
-- 
1.5.4.2