Documentation link - https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/sites/authoring/fundamentals/page-properties.html?lang=en

1.       On-Time – This is the time set on page properties to make a page available at a specified time.

If a page is already published, and on-time is set to a future date/time, this page on Author will lead to a 404 until the specified date/time. On publish for this to take effect the page should be published after setting the on-time.

This is reproduceable on stage.

Eg.

Step 1: set a page, on-time to a future time

Step 2: The page is rendering a 404 as the page is set to a future time to be made available. SS below

Step 3: At 9:42 the page is made available, as per the on-time setting.

Step 4: On publish, this on-time will not make a difference, unless the page is published manually. When the page is set to a future on-time and the page is published the page will not be available on publish as well, renders 404.

Step 5: Once the given on-time is reached, you will not need to publish the page again to make it available on publish. It will be available automatically as per the configured date and time.

2.       Off-time – works very similar to on-time,

Step 1: If a page is set to a future off date, eg, SS below

Step 2: The page is unavailable (renders 404) on author at the set date/time.

Step 3: After the off-time is set to a future date/time and the page must be published, as per the configured off-time publish will take effect, the page will not be made available on publish as well(404 on publish).

Notes :

1.       When on-time and/or off-time is set this appears on the page details as well.

2.       Auto triggers/replication can be configured to publish the page automatically

Details in the below link - https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/operations/replication.html?lang=en#on-and-off-times-trigger-configuration

Such an auto configuration is currently not present in the instance. A future date can be set in author, but the publishing will have to be done manually, so the page availability can be indicated on publish as well.