Windows Phone 3rd party calendar apps facing Microsoft sync glitch (update: fixed)

It seems users of 3rd party calendar apps on Windows Phone are finding they're failing to sync with their Microsoft Live/Hotmail/Outlook accounts.

Apps such as Chronos, Cal and True Calendar 8 are syncing fine with Google accounts and with Microsoft's stock calendar app. But trying to sync with a Microsoft account throw up a fail.

It's believed to be caused by a problem with a Microsoft API, which apps use to communicate with Microsoft services.

A simple temporary workaround is to switch syncing from a Microsoft account to the stock Windows Phone calendar which seems to be unaffected by the bug.

Update: It now seems Microsoft has fixed whatever went wrong and syncing appears to be running normally.