Recently, the phone calendar on my Samsung Galaxy S6 stopped synchronising with Google calendar. When I went to Google Accounts Sync in Settings, Calendar had the spinner next to it, but it was didn’t spin. Meanwhile, the calendar didn’t sync, and the battery was being chewed through more quickly than usual.
How to fix? Well the first thing I tried was deleting Calendar Storage. This worked for a day or two, and then the problem reoccurred. Next, tried deleting all my Google accounts and adding them back. That worked for about a week.
Finally, by a stroke of good luck, I was looking at the sync screen when I’d just plugged in the phone to charge – it synced fine. A lead at last! Likely something related to power settings!
I’d already poked around in the usual Device Maintenance > Battery > App power monitor screen, and all Calendar related apps where in the ‘Unmonitored’ list so wouldn’t be put to sleep. This section wasn’t the cause of the problem. I finally found the solution, in an additional hidden set of power saving options.
So.. To fix, go to Settings > Device maintenance > Battery > Battery Usage button > Vertical … at top right > Optimise battery usage. Choose All Apps from the drop down. Then disable Optimise for Calendar storage and your calendar apps. Voila! Finally calendar will sync reliably again!
UPDATE – Other syncs
I also had a similar issue with Google Sheets, Google Docs and Google Drive Sync. The same change in ‘Optimise battery usage’ settings for each of these fixed their sync as well.