Ok so I just wanted to say thanks for reading this and that I don't own anything that I obviously don't own (characters, places, etc). K so originally I said that Voldemort never came back the second time but then I wrote a chapter mentioning the Battle of Hogwarts and the Second Wizarding War and I didn't even remember that I had said that it didn't happen. Thankfully, Suzululu4moe caught it and DM'd me, so creds to them and I have revamped my background story.
About timing in the worlds and stuff, for Harry Potter this takes place in a world basically where when Voldemort returned the second time none of the important good characters died as a result of him or his Death Eaters (Dumbledore, Fred, Lupin, Tonks, Dobby, etc). So basically everything else not related to death in the books happened and this is set kind of five years after Harry & Co graduated.
For Teen Wolf its basically an AU. When this starts Scott is a werewolf and has been for about a two years (Derek taught him how to control his powers) and he's graduated to True Alpha status and stuff. Scott's mom and Stiles' dad got married and they all live in Beacon Hills, (which in this is a small town in England). They know Derek but he's the only TW character that they know at the start of this fic. Lydia is a banshee and has known for several years now and her mom knows too, Isaac isn't a werewolf yet and Allison knows she's a hunter. It should all be explained in the fic. None of the TW characters live in Beacon Hills besides Scott, Stiles, Derek and their families.
I think that's all you need to know. If you have questions or I missed something please feel free to DM me. Also I really enjoy constructive criticism so feel free to DM me about that too!
Enjoy! :)