Google rolled out a new version of Calendar the other day with support for creating new reminders in the app, but that's not all it seems. Google's App Updates blog explains that there's a new option for syncing your accounts right from the navigation menu.
If you've got sync turned off or something has gone wrong that prevented sync from working, you'll see the message “Enable sync” next to your account in the nav menu. Just tap it and sync will come back online and run instantly. It's a handy way to make sure your events are up to date. Note, you won't see this text at all if sync is working correctly.