diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index d505218c7a0b5fec3ba5ec180a8d5918270ff682..97ffdd88c112b61f284e10c7795122da0c9221ca 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,8 @@
+* Added `Time#days_in_year` to return the number of days in the given year, or the
+  current year if no argument is provided.
+
+  *Jon Pascoe*
+
 * Updated `parameterize` to preserve the case of a string, optionally.
 
     Example:
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 82e003fc3b921db9de490cdea1fc83d5c64e9dd4..675db8a36b02ba69057f185ee331c3db300e7f45 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -26,6 +26,12 @@ def days_in_month(month, year = current.year)
       end
     end
 
+    # Returns the number of days in the given year.
+    # If no year is specified, it will use the current year.
+    def days_in_year(year = current.year)
+      days_in_month(2, year) + 337
+    end
+
     # Returns <tt>Time.zone.now</tt> when <tt>Time.zone</tt> or <tt>config.time_zone</tt> are set, otherwise just returns <tt>Time.now</tt>.
     def current
       ::Time.zone ? ::Time.zone.now : ::Time.now
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index 2d0fb70a6bf3f2752696317a86298b7b95cc10a7..e45df63fd505516116095d688ef59b03e5e61515 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -617,6 +617,25 @@ def test_days_in_month_feb_in_leap_year_without_year_arg
     end
   end
 
+  def test_days_in_year_with_year
+    assert_equal 365, Time.days_in_year(2005)
+    assert_equal 366, Time.days_in_year(2004)
+    assert_equal 366, Time.days_in_year(2000)
+    assert_equal 365, Time.days_in_year(1900)
+  end
+
+  def test_days_in_year_in_common_year_without_year_arg
+    Time.stub(:now, Time.utc(2007)) do
+      assert_equal 365, Time.days_in_year
+    end
+  end
+
+  def test_days_in_year_in_leap_year_without_year_arg
+    Time.stub(:now, Time.utc(2008)) do
+      assert_equal 366, Time.days_in_year
+    end
+  end
+
   def test_last_month_on_31st
     assert_equal Time.local(2004, 2, 29), Time.local(2004, 3, 31).last_month
   end