Why isn't the birthday date from Outlook 'people' option show in 'calendar' (Windows 7)?

[Windows Central Question]

birthdate from outlook 'people' option does not show in 'calendar' (Windows 7)

usually, when I put people's birth date into the 'People' option it updates the birthday calendar in 'Calendar'. But I just came across a case where this did not happen, causing me to miss the person's birthday. What might be the reason that most birth dates copy, but sometimes they don't?

 

[dysje]

It also syncs with Facebook and Skype. And currently especially the Skype integration is known to make a mess of things. I've four birthdays for the same contact in my contact list. The contact doesn't like it when you tell her four times a year Happy Birthday. Apparently.

Perhaps one of the linked networks the contact has set the wrong date. See if you can manually edit this or view this through the outlook.com website.