Why do doctors gestation of a baby is 40 weeks and then turn around and say a woman’s pregnancy only lasts 9 months? Last time I check 40 weeks was 10 months.
The rabbis say that a human being does not get a soul until the 40th day after conception.
It is 10 months, in the sense that it is nine months “inclusive.” It depends whether you count the entire number of months, or rather the number of months “from” the starting time.
This is a confusing thing about counting. Thus, in many languages, a week is referred to as “eight days” and a fortnight as “fifteen”.