https://www.gamespot.com/articles/pokemon-gos-september-community-day-announced/1100-6461167/

Pokemon Go developer Niantic has shared the first details on the game's next Community Day. September's event is scheduled to take place around the world on Saturday, September 22, and it'll feature one of the starter Pokemon from Gold and Silver.

The Grass-type Pokemon Chikorita will be the star of September's Community Day, meaning it'll be much easier to find than usual. For the duration of the event, players will have a greater chance of coming across a Chikorita while they play. The Pokemon will also be able to learn a special move during the Community Day, although Niantic has yet to reveal what it will be.