I'm not sure I even knew what day it was at the time! I'd have a 1 in 5 chance of guessing because I know it was a weekday both times
I often forget DD2's year of birth. Also the exact time they were born - though I could get it correct to the nearest 5 minutes. When DD1 was born, I remember saying about half an hour later that it was a shame I'd forgotten to take note of what time she was born, and the midwife assuring me that it was part of her job to do so!
I don't remember how much either of them weighed either, though I know roughly what it was. I am obviously a terrible mother (who isn't very good at memorising numbers. I didn't know my own date of birth for years, I used to just make it up if anyone at school asked me)
.