Birthdate Question ( FluxCP )

[UniC]

How does fluxcp insert the YYYY-MM-DD format in birthdate, cause when i do it, it is formatted to iso. Thanks.
Edit: ( Making it much clearer )
Was wandering what does fluxcp do in order to save YYYY-MM-DD format to the birthdate column. Because when i did it, using nodejs. It formatted it to an ISO Date. Anyone knows why?

Edited May 9, 2019 by Universe

[Akkarin]

Looking at the code, it's a straight format using the date() function.

date('Y-m-d', $birthdatestamp)