Yes SAO and ACCEL WORLD happens in the same world just SAO incident happens in 2022 and ACCEL WORLD at 2046, and both are amazing time shows

Maybe Death Note and Death Parade are probably in the same timeline too. As it shows in one of the Death Parade episode Light sitting on a chair in the building just waiting but who knows probably just a easter egg.

Doubt it’s Light, he just has the same hair colour.

Technically most Slice of Life anime are in the same universe/timeline.

I’ve heard that Baccano and Durarara take place in the same universe, but you’ll have to confirm that.

So, featuring characters from other anime has no bearing on whether those anime or in the same timeline or universe. They are usually just homages.

One example of different anime that are known to be in the same universe are Steins;Gate and stuff like Chaos;Head, Chaos;Child, and Robotics;Notes...

Yeah, for example Durarara references many anime and light novels like Mahouka Koukou no Rettousei and Toaru Majutsu no Index..there’s even a truck with Miyuki painted on it in DRRR.

Gintama also references a lot of anime.