[Fix #800] Make Rails/TimeZone aware of timezone offset

Author: inkstak

changelog/change_make_rails_time_zone_aware_of_timezone_offset.md

@@ -0,0 +1 @@
+* [#800](https://github.com/rubocop/rubocop-rails/issues/800): Make `Rails/TimeZone` aware of timezone UTF offset. ([@inkstak][])

lib/rubocop/cop/rails/time_zone.rb

@@ -55,7 +55,7 @@ class TimeZone < Base
 
         ACCEPTED_METHODS = %i[in_time_zone utc getlocal xmlschema iso8601 jisx0301 rfc3339 httpdate to_i to_f].freeze
 
-        TIMEZONE_SPECIFIER = /[A-z]/.freeze
+        TIMEZONE_SPECIFIER = /([A-z]|[+-]\d{2}:?\d{2})\z/.freeze
 
         def on_const(node)
           mod, klass = *node
@@ -126,7 +126,7 @@ def check_time_node(klass, node)
         end
 
         def attach_timezone_specifier?(date)
-          date.respond_to?(:value) && TIMEZONE_SPECIFIER.match?(date.value.to_s[-1])
+          date.respond_to?(:value) && TIMEZONE_SPECIFIER.match?(date.value.to_s)
         end
 
         def build_message(klass, method_name, node)

spec/rubocop/cop/rails/time_zone_spec.rb

@@ -123,6 +123,18 @@
       RUBY
     end
 
+    it 'does not register an offense when attaching timezone offset' do
+      expect_no_offenses(<<~RUBY)
+        Time.parse("2012-03-02 16:05:37 +0100")
+      RUBY
+    end
+
+    it 'does not register an offense when attaching timezone offset using a colon' do
+      expect_no_offenses(<<~RUBY)
+        Time.parse("2012-03-02 16:05:37 +01:00")
+      RUBY
+    end
+
     it 'registers an offense for Time.at' do
       expect_offense(<<~RUBY)
         Time.at(ts)