question

The deferral is a measurement from when the update is released by Microsoft. So two days means 2 days from 1000 PST (typically) on the day the update is released (the 2nd Tuesday of the month typically).

Similarly, the deadline is a measurement from when the deferral expires or when Microsoft releases the update if no deferral is specific.

It's not random, but yes, it is linked to the update detection frequency which is every 22 hours: see https://docs.microsoft.com/en-us/windows-server/administration/windows-server-update-services/deploy/4-configure-group-policy-settings-for-automatic-updates#automatic-updates-detection-frequency.

Thus, the deferral and deadline times for a system must be in the past at the time an update eval takes place.

@StphaneLalancette-1501

Thank you for posting in Microsoft Q&A forum.

Deferral days are calculated against the release date of the chosen channel. Starting with Windows 10, version 1903 there is only the one release channel: Semi-annual Channel. All deferral days are calculated against a release’s Semi-annual Channel release date.

For more details, please refer to this article:
https://docs.microsoft.com/en-us/windows/deployment/update/waas-manage-updates-wufb

Have a nice day!

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Hi, thank you for the follow-up.

I think it answers my question, but what would be the best way to know when the scan actually happens?

Asking, because. coming from sccm world, we have logs and reporting that show when all of this happens and also specify when the update will be visible for clients to install and enforce. So we would like to know a bit more detailed information as to when users/clients could expect updates to appear/install.

I guess we can say that it's best to count an extra day from what we set to know when the deferal and deadline to really be applied for sure on all devices?

For the deadline, if we specify 2days, is it 2days (48hrs) after the client saw that the deferal is pasted last time it scanned? or will it be 48hrs plus the next time the device will scan?

Thank you in advance

> is it 2days (48hrs) after the client saw that the deferal is pasted last time it scanned?

No, as called out above, "the deadline is a measurement from when the deferral expires or when Microsoft releases the update if no deferral is specific." Scan time is not relevant here (or in ConfigMgr for that matter).

WindowsUpdate.log is your source for detailed information and the Windows event log is also useful as ultimately, WUfB is nothing more than standard Windows Update.

Sorry, I meant that since the time/day the deferal starts depends on when the clients scans and it's not the same on all systems and if the scan happens a few mins before MS release the patch tuesday updates, it can be an extra 22hrs, compared to a system that scanned fro updates a few mins after they where released.

In that example, am I right in saying that the two systems would have a deadline just shy of 22hrs appart?

Asking because at the moment, we enforce the updates on the last Sunday of each month at 9PM, so since with WUFB deadline, we can't be as specific as that, we want to know as much as possible when we can expect all of this to happen.

Thank you again for all your detailed information and taking the time to clarify my missinterpretation.