Quoting this post from the last thread by snooptroop88:
Gilgo Beach LISK Serial Killer, Rex Heuermann, charged with 6 murders, July 2023 #14
I have a feeling that this will become one of those things that's very obvious in hindsight, and maybe that's meaningful to him but not really a significant date to anyone else out of context. If he was changing the year to be a birthdate, why not use his actual year? Unless he was trying to shave years off his age, which is certainly possible.
My own theory, with no way whatsoever to prove it unless he starts talking, is it was when he first started hunting - probably not an actual hunting trip, because for a lot of animals hunting season is later in the fall, but maybe when he got his first rifle or took a hunter safety course or something.
Among a lot of hunters, it seems like 8-10 is around the age they start taking their kids, and he really seems to identify himself as a hunter (maybe even Hunter with a capital H). He's a member of hunting clubs, he tells everyone about hunting ducks or deer or apparently bears, he would invite colleagues to go hunting. I happened to rewatch the 20/20 episode on his arrest a couple days ago and a source on there mentioned that he was especially interested in serial killer Robert Hansen, who hunted his victims in the Alaskan back country. I think he sees hunting as a core part of his personality - both hunting animals, and hunting his victims - and that date might tie into that somehow.