https://www.polygon.com/2017/10/19/16501282/pokemon-go-halloween-event-2017-date-gen-3-new-pokemon

Pokémon Go will feature a batch of new Pokémon for players to catch starting this week, Niantic confirmed. To coincide with this year’s in-game Halloween promotion, five Pokémon from the series’ third generation of monsters will begin appearing worldwide.

The Halloween event kicks off at 12 p.m. PT on Oct. 20 and runs until Nov. 2 at 1 p.m. PT. During this timeframe, players will run into increased numbers of several ghost-type or just generally “spooky” Pokémon like Gengar, Cubone and Misdreavus. But they’ll also get their first opportunity to collect Pokémon from the Hoenn region, the setting of 2002’s Pokémon Ruby and Sapphire. These will all be ghost-type Pokémon, including Dusclops, Sableye and Shuppet.