@RasitAyaz said:
People's birthdays go one day back when editing the page
I noticed this weird behavior when editing some people's pages. For example, Bryan Cranston's birthday appears as 1956-03-07 in his page. But when editing, it appears as 1956-03-06. Interestingly, this does not happen on everyone's page.

The Date Bug

Yes. It's a Bug. A mysterious Bug that's been around for a long time.
And to this day Administrator Travis Bell has not been able to identify the cause. :-)
Code Programming Mysteries.

It occurs with greater regularity on older dates.
Anyway, I believe that, for cases like this, the rule is:
When you identify the issue, enter the date one day earlier.
Thus, for Site users the display will be the correct date.
And in API Requests the answer will also be the correct date.

I've personally followed code programmers
racking their brains trying to solve these minor and annoying issues.
Months without finding out why.
Then, one fine day, the explanation arises.
One more comma, one less space, one Plural when it should be Singular.
Or the Vice Versa of it all.
And everyone wants to fall off the Empire State or jump in front of a Train.
The Greatest Anger and the Deepest Hate when they discover the reason.
But in the end, all we can do is laugh. :-)

Just noticed your reply and it made me smile, thank you. I'm also a developer myself so I'm familiar with these kind of things.

I recall that where an editing user is located seems to determine what date will appear. Five or so years ago, ticao and I were working together (incidentally, we're in different parts of the world) on improving a profile page, he stated to me he was seeing a particular birth day for the celebrity, tho simultaneously I was seeing one day earlier (or maybe it was one day later).

Well remembered Genplant. :-)