Scheduling and managing events using Outlook.com calendar
Did Microsoft ever get anywhere with this problem? I'm getting the same issue - birthday clearly visible on a contact, but does not appear on calendar either online or on the phone. And yes I do have birthday calendar switched on! Other birthdays appear!
As you said, it's no good if it doesn't work reliably, and it ought to be dead easy. All it needs is a program that would trawl through your contacts, pick up their birthdays, and put the dates on your calendar...ought to be a doddle.