HA!! I did the same thing tonight.
I had an alarm set for hearing today, but got busy at work, so set it for tonight so I could catch up...darn it...it was rescheduled.
I've beaten ya! I turned up yesterday (13) couldn't find a thing so checked my diary and noticed I'd got it for today. To make sure I came here and looked back 2 pages and saw a post say it's the 17th. Turned over to next page it's the 21st now.
I remember the date changing, but where I originally wrote the date I have no idea BUT I have got her in for the 21st. Don't remember writing that.