Q: Why won't my calendar sync after Yosemite update.

This worked for me, too.

In Step 1 I still had the problem.

In Step 2, I did not have the problem of losing the change.  (I have another problem of the calendars not syncing between iMac, Macbook Pro and iCloud.)

After rebooting, normal mode, I still had the problem.

Any thoughts?

I have no other calendar accounts in use.  I just use iCal and iCloud between my computers.  It worked fine before I updated both machines to Yosemite.  I've also tried deleting my iCloud account in System Preferences and re-establishing it but that didn't help either.  One interesting thing I see when I log onto iCloud on the Web via Safari is, under settings it only shows my MacBook Pro under "My Devices".  Of course, I don't think this is related as I have the problems of lost changes and no syncing on both machines.

Thanks in advance for your time.

Paul

Thanks man it really worked. But how can it be possible? I got an Iphone with the same iCloud account and there is a one pair of macbook and iphone too which they have a same account different from me.

I figured that out, you have to sign out from your iCloud on macbook then sign in. Your iPhone will get those updated events.

I found an easier way to so force the iPhone to sync with iCloud. In the Calendar app on the iPhone, click the Calendars button. On the next screen, where you have your list of calendars, just drag the list downward. That refreshes it, and you should see a momentary spinning circle at the top. Voila! All the changes you made on your mac should now be on the phone.