Because the timeliness of paternity/maternity leave is determined by the childbirth's date, not by anything else.

That's obvious to anyone who knows how humans replicate.

The sentiment of the comment was that the timing was unfortunate because the kid was born in the same period that had presumably something else going on on the work side. Not that the child was born. So either the OP had some prior "history" with his manager, which changed the literal meaning of the comment, or he is reading too much into it.

What is the childbirth's date roughly determined by? There's an event that must occur before childbirth is even possible.

Are you legit suggesting that people should do their family planning around their employer's convenience?

Is that how you read my comment? Odd, because that's not what I wrote at all. The comment I replied to suggested that the timing of a child's birth was completely random and unpredictable. I suggested that's not the case. I don't know how you got from what I wrote to what you read, that's quite a mental leap!

so you wrote it to just state the obvious and in no way to imply that i should've planned conception around my future promotion attempt? got it.