In case you didn't know.
Summary:
Legion opens at 12am PST
All dungeons normal and heroic 12am Mythic 8am
PVP Season Sept 20
Emerald Nightmare Raid Normal and Heroic Sept 20
Raid finder for wing one and Mythic Sept 27
Wing two raid finder Oct 11
Wing three raid finder Oct 25
https://worldofwarcraft.com/en-us/news/20243893/world-of-warcraft-legion-release-schedule