A small but potentially annoying problem: on rare occasions, your iPhone/iPad may decide your calendar looks full enough and will stop syncing with your Google calendar. This is a situation where:

1. Calendar sync between your iDevice and Google used to work yesterday, but doesn’t work today. If your sync never worked, this article is not for you.
2. Your iDevice is still able to sync email with your Gmail account. If your email sync doesn’t work either, the solution below will not work for you. Your problem is likely incorrect password or lack of network access.

And so, recently I noticed that a few calendar events I created on my iPhone did not make it to my Google calendar and vice versa. As a result, today I overbooked myself and ended up joggling customer meetings. After googling for solutions and not finding any that worked for me, I had to get creative. The process that worked for me is below.

However, before you try it, may I suggest on your iDevice, going into Settings –> Mail, Contacts, Calendars –> scrolling all the way to the bottom and making sure that your “Default Calendar” is set to the appropriate Gmail calendar and not to, say, iCloud. By the way, if the latest one won’t open – here is the iCloud removal assistant.

Also, keep in mind that, if you used a third-party calendar app on your iDevice (I use Week Cal, for example) to create events, all customized colors, icons, etc. will be lost when you re-import those events from Gmail. Bummer, I know.

1. On your iDevice, go to Settings –> Mail, Contacts, Calendars
2. Select the first Gmail account for which you have “Calendars” enabled for sync
3. Disable “Calendars” sync option. You will be warned that all related calendar events will be removed from your iPhone/iPad. Agree and continue.
4. It will take your iDevice a few seconds to remove related events from your local calendar.
5. Repeat steps 2-4 for each Gmail account for which you have “Calendars” enabled for synchronization.
6. Now if you go to you iPhone/iPad calendar, it will be largely empty, except for any events created locally or synchronized from other, non-Gmail accounts.
7. All you have to do now is to repeat steps 2-4, but this time you will enable “Calendars” for sync.
8. Re-open your iPhone/iPad calendar app and it may take a minute or more for it to re-download the events from all your Gmail calendars.
9. As a last step, you may want to verify that sync is working by creating a test event locally on your iPhone and checking a bit later if it appeared on your default Gmail calendar.

Why this problem occurs in the first place – I have no idea. Some bug on Apple’s side, I would guess, but I am not an entomologist, so don’t press me on details. Hope this works for you.