Ok, I am pretty sure I am being unreasonable but sure anyway!
It has always bugged me when friends have said 'it's actually 10 months you're pregnant for' with a sort of in the know grin. I had 1 in particular go on about it when she was pregnant that all of the world has had it wrong since we started recording these things. But it's not. It is 9 months. I have heard several other women saying it in different settings.
I get where her maths is coming from 40 weeks/ 4 = 10 months.
BUT most months do not stop at 28 days.
If that was the case 52 weeks/ 4 = 13 months I am not aware of a 13th month in the year.
22nd May to 22nd June you would say is one month away, not one month and 3 days. Those 3 days p/m over a pregnancy adds up to 27 days.
My LMP was October, my baby is due this July, by my count that is 9 months.
Yes I know little to be worrying about and yes I can get pedantic. No I do not and have not ever countered a pregnant woman who says pregnancy is 10 months IRL.