You must set a Death Stranding birthday when you start the game, with the message "DOOMs abilities vary according to date of birth". That definitely makes it sounds like there could be a best possible birthday, but what is the best date? And what does DOOMs actually do?
It's an utterly vague system in Death Stranding, so I've explained everything I know about it below to help you decide on when to set your birthday so you stop worrying about it all. The important thing is that it's not really that big a deal, just a fairly inconsequential beat in a weird game that happens to pop up right at the start to make you start questioning things about the game's world.
