Note : This is only for things that I think will be good to know starting off, it's not noting every major change
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-Obviously Golderoy is a transmigrated soul, the soul took over when in January 1985 very soon after the original Lockhart published his first stolen book
-Gilderoy graduated 1 year later than in cannon so in 1983
-After Gideroys first book his next ones are real accomplishments
-Tonks will graduate 2 years later than cannon so she's still in Hogwarts during the second book
-Hogwarts admission will now be 3 years later than cannon, but everything will still happen in the same years, so all cannon characters, except for Tonks and Gilderoy and Tonks who are 1 and 2 years younger respectively, will be born 3 years earlier