The "All Day' Calendar events on my Office 365 account, are all showing a day early on my Samsung S9. My regular calendar entries are all ok.
1. Its not the Office 365 account as..... My old Samsung S7 is showing them correctly. My Outlook on my pc is showing them corrently. The Outlook Web App is showing them correctly. I have tried a second Office 365 account too, and the Holidays calendar (which has all 'All Day' events) has the same problem.
2. It is not a date issue on the phone, as..... All my regular calendar entries are showing correctly. My Google account calendar sync is showing correctly. My Google account calendar sync is showing the All Day events correctly too.
3. It is not the calendar app as...... I have tried multiple different calendar apps on the S9 and they all show the same info.
4. Per support, I have tried.... Resetting the app preferences. Deleting the app cache. Wiping the cache partition.
I believe the issue has to do with the way the S9 is syncing EAS (activesync) calendar data, specifically with All Day events.
This is the most recommended action. Unfortunately it is not a solution.
I don't have this problem and I synchronise both mine and my wife's outlook calendars to our phones. However, it strikes me that this might be caused by a mismatch of time zones somewhere along the line. I suggest that you check that Office 365 and your phone are set to be in the same time zone (though if this is the case and you correct it, it may screw up your currently correct entries).