I took the very first value in HxD (block 00 in offset 0) and changed it to 01, but after opening in PKHeX and saving, my checksum did not change. Why would this be?
And thanks!
EDIT: I did, however, get the checksum to 00 F5 by changing my TID to 44405 (and keeping my SID the same at 40171). How can I tell if this is a valid TID/SID combo given the vast amount of seeds that could be obtained with a live battery? The only way I can think of is to search each minute of each hour of each calendar day, which is impossible.
EDIT2: I got the checksum to 00 F5 by changing my game time to 5 hr 26 min 30 sec.
EDIT3: I GOT IT! Thanks everyone for all your help!