I am on Microsoft Outlook for Microsoft 365 MSO (16.0.13127.21452) 64-bit but had this problem for other Outlook versions also.
Problem
I would expect the Microsoft Outlook to pop up at exactly MM:00, however, they always pop up at around MM:44 or MM:45. For example, if I create a meeting for 09:00 CEST with a reminder 15min before I will get the reminder pop up only at ~08:45:45. And if say remind me again 0 minutes before the meeting, I get the reminder pop up at ~09:00:45. I would expect to get the reminders at 08:45:00 and 09:00:00.
Exclusion of potential source of errors
Since I've had this behavior in two different companies now I do not suspect server error with time synchronization (if the server even has anything to do with this). I have regular NTP updates and my time matches e.g. with https://time.is/ (however, I guess the Outlook client just takes the OS time so this should also not be a problem). Could only be a problem with the client somehow not handling CEST correctly but I would have no idea why there would be a 45s delay.
Question
So I am wondering, is there a setting that I am missing in Outlook that I can change to get the reminders always at MM:00? Or is this known intended behavior?
Used workaround for now
I just use the workaround for now to have a default reminder of 17 minutes before the meeting (works only for newly created/accepted meetings) and then remind in 15min again so I am roughly reminded at 08:58:45. However, if I do not click instantly, in 15min might be too late as to my understanding it is 15min from the time I snoozed the reminder, not when it originally popped up. So I am then left with a reminder much earlier or clicking 0 minutes before the meeting which is too late. Hence my question above.