Why is iCloud not syncing my calendars on my iOS devices?

When I create or update a calendar event on one device, it is not being propagated to my other devices via iCloud despite having iCloud enabled for calendars on all my devices and the Apple ID being the same everywhere.

Your iOS device may be saving new calendar events to a local calendar instead of the iCloud calendar. This is particularly confusing if that local calendar has the same name as the calendar you want to use in iCloud. To change the default calendar for saving events on an iOS device, navigate to Settings > Mail, Contacts, Calendars > Default Calendar and select your preferred calendar under your iCloud account:

Problem: Synching a shared calendar did not work from my Mac to iPhone (using iCloud), but worked from iPhone to Mac.

What I did: In the Calendars App on the Mac I exported the calendar - to have it as a backup. The old calendar could not be deleted on the Mac, it just re-appeared again (confirming that changes made on the Mac did not sync to iCloud). I therefore deleted the old calendar on my iPhone and it disappeared on the Mac as well. Good.

Then I re-imported the exported (old) calendar and gave it a new name. It now works. Probably would work using the old name as well (since internally the app uses calendar-IDs).

Try this:

1. Turn off the iCloud calendar on the phone: Settings> iCloud> Calendar> Off
2. Do a hard reboot of the phone: Hold down Power & Home buttons simultaneously.
3. Turn on the iCloud calendar on the phone: Settings> iCloud> Calendar> On
4. Set the phone and computer calendars to Push. ON PHONE: Settings> Mail> Contacts> Calendar> Fetch new date - turn push on then under the iCloud mccs + 6 more, set to push ON COMPUTER: in Calendar app> Preferences> Accounts> iCloud> Refresh calendars - set to push
5. Refresh the iPhone calendar. In the Calendar app, go to Calendars and drag the screen down for a refresh.

Now it should work.

If some events are still not showing after the previous advice, left click on the event in question (on the calendar on your Mac). Then click on >Calendar on the drop down; if the event type shows under "on my mac", select the same colour under the "iCloud" portion Next refresh your phone calendar as per above, by swiping down on the (daily) notes section of the calendar app. The event should now appear on both phone and Mac.

I had this problem and turned out that a setting had been put in place to only sync calendars 1 month back (Go to Settings. Mail, Contacts, Calendars. Sync. All Events)

So I could not see my data from prior months even though it was there in iCloud. I changed it to Sync All Events, turned phone off then on, and voila.