Scheduling and managing events using Outlook.com calendar
Hi
The "solution" I found is delete this lame calendar as the service is obviously not functional, since months ! A habit at Microsoft, not to solve some problems for years ! (for instance : "Outlook keeps on asking for credentials" : bug existing since Outlook 2003, and still in Outlook 2013, 12 years without solving a bug ! World Record !)
For the record, I also gave up with my Windows Phone : too many sync issues (OneDrive documents, contacts, birthdays, etc.).
For now, I check birthdays on my iPhone. It works perfectly... And any change is pushed within seconds.