This members-only tutorial provides the steps to register a custom condition in Oxygen using which elements will stop being output on the front end after the specified date (and time).
This is useful for displaying say, a promo bar above the site header only during the sale period.
The reasons why you might want to use this instead of the built-in Date and Time conditions in Oxygen are because the following are still valid as of Oxygen 4.0.1 RC 1:
Step 1
Create a new code snippet using a plugin like WPCodeBox.
Title: [Condition] Don't Output After (or) Expires On