iCloud Reminders Syncing Issue [Fixed]
15 Aug 2021
For the last many many months, I would have issues with iCloud Reminders syncing well between my imac, macbook, ipad and iphone. I had to "complete" the reminder on all devices and this was truly frustrating. I tried all the usual troubleshooting tips (log out of all devices, log back in etc.) but the thing that worked for me was to make sure your Timezone and time formats are all the same across all devices.
Login to icloud.com -> Account Settings → Timezone / Formats
Make sure the formats match your other device formats. My time format was off and by fixing this the syncing works like a charm :)
Good luck!