I just don't even get threads like this. If my husband said that to me I'd just say no, sort it out. Why on earth can't you just speak to him?
Precisely. I'm shaking my head at this thread. If (general) you can't say something like this to your own spouse, who can you can say it to?
You have way bigger problems than being double booked on your birthday. Start off by sorting out how to communicate with your partner for a start.
This type of situation/conversation is such a non-event:
Spouse 1: Hey, are you free on Saturday to do Y?
Spouse 2: No, I'm doing Z - it's on the calendar/I told you already.
Spouse 1: No worries. I thought we might do (event), but I'll rearrange it for another day.
Spouse 2: Okay. I'll look forward to it on (other day). Hey, did I tell you what happened at work today....
Also, if I was your friend, I'd have been severely pissed off at having our/my event hijacked like that, especially when you had the power to stop it.