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
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Step 2: The page is rendering a 404 as the page is set to a future time to be made available. SS below
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Step 3: At 9:42 the page is made available, as per the on-time setting.
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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.
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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.
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2. Off-time – works very similar to on-time,
Step 1: If a page is set to a future off date, eg, SS below
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Step 2: The page is unavailable (renders 404) on author at the set date/time.
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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).
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Notes :
1. When on-time and/or off-time is set this appears on the page details as well.
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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.