Me : I don’t get it. I know my LMP* was on a Saturday, so how come each new week starts on a Sunday?
Midwife lady : you’re right
Me : ah, good
Midwife lady (thinks, probably) : and a bit pedantic, too

Later on

Me : okay, so if I’m 13 weeks and six days, then how come I’m 14 weeks on Sunday?
Shaun : eh?
Me : Well, tomorrow I’ll be 13 weeks and seven days! See! It doesn’t make sense!
Shaun : there’s seven days in a week…
Me : ehhhh?
Shaun : you’ll be 14 weeks, tomorrow. 13 weeks, and seven days, is equal to 14 weeks.
Me : ohh yesssssss

(baby brain fail)

* google it