How To Make Blocks Disappear on Certain Date/Time

A well written plugin can still function properly without being updated. Or it can fail horribly. It all depends on what it actually does. There’s a chance it will still work fine, but since it is no longer supported, it’s up to you to ensure it works as expected, and to correct any errors that may crop up. Not a good choice unless you have some PHP coding experience.

My alternative suggestions also require either PHP or JS coding. One approach would be to schedule tasks through wp_schedule_single_event() that first adds in the desired HTML into existing content, then another event task to remove the same HTML at the specified time. Keep in mind that the tasks cannot be accurately scheduled to the minute. The event firing is dependent upon someone or something making a request to your site after the specified time before anything actually happens.

Alternately, you could hook into “the_content” filter and have your callback insert the HTML if it is between the specified times. This could also be handled as a shortcode or editor block.

Which to chose depends in part on if it’s important to have the correct content as it sits in the DB, or if it’s OK to correct the content on the fly when the post is requested.