A common case even in stable, industrialised, first-world nations. Bottom line, it’s a false assumption that everyone knows the date or even year of their birth, quite apart from being willing to disclose it or able to prove it.

I can also reveal that parents routinely mix up the DoB of their kids, and the more kids they have the worse this becomes, and I realised at some point during my association with club-level sport that it is a direct consequence of how tired they are