Key point: Credence/Aurelius was not born in 1901
Well, with my previous theory(linked below) that Credence can age backwards, it's now obvious Rowling can put his birth year to be in any year.
https://harrypotter.fandom.com/d/p/3343172654596353805
Now let's just try to figure out his actual birth year and see how we can explain as why he was not born in 1901.
According to wiki and the screenplay, Credence alleged birth year was 1901(not solid, remember, it's alleged date), though his adoption certificate documents him to be born in 1904. See the image below:
Confusing, right? Which one is true? 1901 or 1904? I would say, neither.
Considering the babies were swapped in the ship, anyone would assume that the adoption certificate documents Corvus's birth year actually.
But hey, the ship incident occured in 1901 then how come the adoption certificate documents the birth year of Corvus to be 1904? He was supposed to be born in 1901,right?
Here's the reason, why?
What I theorise now is that Irma Dugard soon found out that the child she saved was not Corvus but Credence. It's specifically said in the screenplay that it was the rush on the ship cuz of which she failed to recognize him at the moment.
Also, you must note Irma knew Credence's aunt and so would have known Credence as well. Which means, she recognized the baby with his real identity later.
Here's the proof from Screenplay where Credence's aunt addresses Irma:
CREDENCE’S AUNT
Irma? They want us to put on life jackets!
Irma didn't immediately submit the baby Credence to Mary Lou. She raised him for about four years and then in 1905, she submitted the baby to the orphanage.
But as, there were no changes in Credence's body during this time, she wrote him to be born in 1904 in his adoption papers to avoid any suspicion. Probably, during these years, she helped the baby grow forward as well which helped Credence grow normally thereafter.
This is the reason why Credence's or more specifically Corvus's adoption papers had 1904 written as his birth year.
This makes sense why Rowling killed Irma, she would have told Credence the whole story after all.
This makes us wondering, what's the actual year of his birth then?
I have chosen the year 1898, for him. There are reasons why I chose this year but I would be explaining that in my next post.