The PublishPress Future plugin allows you to schedule automatic changes to posts, pages, and other content types.
With this plugin, you can create automatic actions to unpublish, delete, trash, and sticky a post. It also allows you to create an automatic action to change the status, update the categories and much more.
You can create new automatic actions using the PublishPress Future metabox that looks like this image below. You can see that the time in the box is 12:54, which uses the 12-hour format, rather than a 24-hour format.
By default, PublishPress Future is showing the time in a 12-hour format, and then adding AM or PM. That's because PublishPress Future is pulling the setting from the default WordPress time format setting. The default time format is shown in the image below. You can find it by going to “Settings” and then “General”. This is the default format:
In order to change this so it shows in 24-hour format, you can use the “Custom” option, as in the next image below. This will change the format used everywhere on your WordPress site.
After you change this setting, the PublishPress Future box will not show AM:PM anymore and you can use the 24-hour time format.
More with PublishPress Future Pro
With PublishPress Future Pro you can get more features to help schedule changes to your posts. You can see a log of all the changes to your posts, and you can also schedule posts to move to custom statuses.