Add Change The Time Zone Offset Of A DateTime Object as a rails til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -638,6 +638,7 @@ _1060 TILs and counting..._
 - [Capybara Page Status Code](rails/capybara-page-status-code.md)
 - [Cast Common Boolean-Like Values To Booleans](rails/cast-common-boolean-like-values-to-booleans.md)
 - [Change The Nullability Of A Column](rails/change-the-nullability-of-a-column.md)
+- [Change The Time Zone Offset Of A DateTime Object](rails/change-the-time-zone-offset-of-a-datetime-object.md)
 - [Check If ActiveRecord Update Fails](rails/check-if-activerecord-update-fails.md)
 - [Check Specific Attributes On ActiveRecord Array](rails/check-specific-attributes-on-activerecord-array.md)
 - [Code Statistics For An Application](rails/code-statistics-for-an-application.md)

rails/change-the-time-zone-offset-of-a-datetime-object.md

@@ -0,0 +1,27 @@
+# Change The Time Zone Offset Of A DateTime Object
+
+Let's say you have a timestamp string that you parse with
+[`DateTime.parse`](https://ruby-doc.org/stdlib-2.6.1/libdoc/date/rdoc/DateTime.html#method-c-parse).
+
+```ruby
+> DateTime.parse('2021-02-23T11:59:11')
+#=> Tue, 23 Feb 2021 11:59:11 +0000
+```
+
+Without the specification of a time zone offset in the timestamp string, it
+will be parsed as UTC.
+
+If you want to change it to another time zone, you can alter the `offset`
+option of the `DateTime` object. Rails provides the
+[`#change`](https://api.rubyonrails.org/classes/DateTime.html#method-i-change)
+method for doing this.
+
+```ruby
+> DateTime.parse('2021-02-23T11:59:11').change(offset: '-600')
+#=> Tue, 23 Feb 2021 11:59:11 -0600
+```
+
+By changing the `offset` to `-600`, the `DateTime` now represents a time in
+Central Time.
+
+[source](https://stackoverflow.com/a/47861810/535590)