Retain UTC offset when using Time.at_with_coercion

The standard Ruby behavior for Time.at is to return the same type of
time when passing an instance of Time as a single argument. Since the
an ActiveSupport::TimeWithZone instance may be a different timezone than
the system timezone and DateTime just understands offsets the best we
can do is to return an instance of Time with the correct offset.

Fixes #11350.

1 files changed, 8 insertions, 3 deletions

diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 8270093dc7..20e7e0b303 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -33,10 +33,15 @@ class Time
     # Layers additional behavior on Time.at so that ActiveSupport::TimeWithZone and DateTime
     # instances can be used when called with a single argument
     def at_with_coercion(*args)
-      if args.size == 1 && args.first.acts_like?(:time)
-        at_without_coercion(args.first.to_f)
+      return at_without_coercion(*args) if args.size != 1
+
+      # Time.at can be called with a time or numerical value
+      time_or_number = args.first
+
+      if time_or_number.is_a?(ActiveSupport::TimeWithZone) || time_or_number.is_a?(DateTime)
+        at_without_coercion(time_or_number.to_f).getlocal(time_or_number.utc_offset)
       else
-        at_without_coercion(*args)
+        at_without_coercion(time_or_number)
       end
     end
     alias_method :at_without_coercion, :at