why the date difference on this pet?

[polymer]

so i got this pet from the pound earlier and i was excited to get something from 2009, so i went back and checked the archives and it turns out this pet was actually from november of 2008 and not march 2009 as the adoption date says. i wasnt sure how to find the answer to this without making my own post about it. its probably that the site just operated differently back then but i'd love to know how exactly that happened!

the pet in question for reference:

[Horror]

It’s what’s known as an extended release pet. Back then they didn’t always immediately swap all out all the pets for new ones at the top of each month and some (like that dog and it’s litter) were available to adopt for a super long time ^^