Fix bug that causes TimeZone.seconds_to_utc_offset to returns wrong offset...

Fix bug that causes TimeZone.seconds_to_utc_offset to returns wrong offset when hour < 0 and not in hundreds [#3741 status:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

activesupport/lib/active_support/values/time_zone.rb

@@ -172,7 +172,7 @@ class TimeZone
       MAPPING.freeze
     end
 
-    UTC_OFFSET_WITH_COLON = '%+03d:%02d'
+    UTC_OFFSET_WITH_COLON = '%s%02d:%02d'
     UTC_OFFSET_WITHOUT_COLON = UTC_OFFSET_WITH_COLON.sub(':', '')
 
     # Assumes self represents an offset from UTC in seconds (as returned from Time#utc_offset)
@@ -181,9 +181,10 @@ class TimeZone
     #   TimeZone.seconds_to_utc_offset(-21_600) # => "-06:00"
     def self.seconds_to_utc_offset(seconds, colon = true)
       format = colon ? UTC_OFFSET_WITH_COLON : UTC_OFFSET_WITHOUT_COLON
-      hours = seconds / 3600
+      sign = (seconds < 0 ? '-' : '+')
+      hours = seconds.abs / 3600
       minutes = (seconds.abs % 3600) / 60
-      format % [hours, minutes]
+      format % [sign, hours, minutes]
     end
 
     include Comparable

activesupport/test/time_zone_test.rb

@@ -208,6 +208,12 @@ def test_seconds_to_utc_offset_without_colon
     assert_equal "+0000", ActiveSupport::TimeZone.seconds_to_utc_offset(0, false)
     assert_equal "+0500", ActiveSupport::TimeZone.seconds_to_utc_offset(18_000, false)
   end
+  
+  def test_seconds_to_utc_offset_with_negative_offset
+    assert_equal "-01:00", ActiveSupport::TimeZone.seconds_to_utc_offset(-3_600)
+    assert_equal "-00:59", ActiveSupport::TimeZone.seconds_to_utc_offset(-3_599)
+    assert_equal "-05:30", ActiveSupport::TimeZone.seconds_to_utc_offset(-19_800)
+  end
 
   def test_formatted_offset_positive
     zone = ActiveSupport::TimeZone['Moscow']