In game, the current season is said to end on August 7, 2017 (Monday).
https://api.guildwars2.com/v2/pvp/seasons/2F306FFD-500A-45E3-9118-1F0831F1B89F
I checked the api key and it said that it ends on August 8, 2017 (Tuesday) at 0:00 or 12am, is it 12am in server time?