Merge pull request #35659 from rails/fix-time-advance-with-historical-dates

Fix Time#advance to work with dates before 1001-03-07

3 files changed, 17 insertions, 2 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index b2330f2c9d..63e2e44597 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,17 @@
+*   Fix `Time#advance` to work with dates before 1001-03-07
+
+    Before:
+    
+        Time.utc(1001, 3, 6).advance(years: -1) # => 1000-03-05 00:00:00 UTC
+    
+    After
+    
+        Time.utc(1001, 3, 6).advance(years: -1) # => 1000-03-06 00:00:00 UTC
+
+    Note that this doesn't affect `DateTime#advance` as that doesn't use a proleptic calendar.
+
+    *Andrew White*
+
 *   In Zeitwerk mode, engines are now managed by the `main` autoloader. Engines may reference application constants, if the application is reloaded and we do not reload engines, they won't use the reloaded application code.
 
     *Xavier Noria*
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 120768dec5..f09a6271ad 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -170,8 +170,7 @@ class Time
       options[:hours] = options.fetch(:hours, 0) + 24 * partial_days
     end
 
-    d = to_date.advance(options)
-    d = d.gregorian if d.julian?
+    d = to_date.gregorian.advance(options)
     time_advanced_by_date = change(year: d.year, month: d.month, day: d.day)
     seconds_to_advance = \
       options.fetch(:seconds, 0) +
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index 7078f3506d..590b81b770 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -514,6 +514,8 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal Time.local(1582, 10, 15, 15, 15, 10), Time.local(1582, 10, 14, 15, 15, 10).advance(days: 1)
     assert_equal Time.local(1582, 10, 5, 15, 15, 10), Time.local(1582, 10, 4, 15, 15, 10).advance(days: 1)
     assert_equal Time.local(1582, 10, 4, 15, 15, 10), Time.local(1582, 10, 5, 15, 15, 10).advance(days: -1)
+    assert_equal Time.local(999, 10, 4, 15, 15, 10), Time.local(1000, 10, 4, 15, 15, 10).advance(years: -1)
+    assert_equal Time.local(1000, 10, 4, 15, 15, 10), Time.local(999, 10, 4, 15, 15, 10).advance(years: 1)
   end
 
   def test_last_week