Anniversary update clears event log, known behavior?

Hello Loc2262 and welcome to TenForums :)

Yes this is normal behaviour, in effect the Anniversary update is a new installation so all the events log are newly created. The old logs will be found in the Windows.old directory which remains in place for about 10 days so that you can revert to the previous version if you so wish.

After about 10 days Microsoft assumes you will want to keep the update and so it deletes all the old files and recovers the disk space for you.

Hello Phil and thanks for your extensive reply!

Roger that, good to know it's expected. I was thinking it might be something like that, considering also the update history list gets cleared (which Google results already implied to be expected).

The "Windows.old" is already gone; it's been more than 10 days. But that's no problem; knowing not to trust MS updates, I took an Acronis backup right before I installed the Anniversary.

Thanks again! (There's no "kudos" button on this forum, is there?)

You are welcome. You can read about the reputation system we use here: Reputation and Badges

Aah okay, I found the "thumbs up" Icon to add to your reputation now. :)