The next Pokémon GO Community Day is set to take place on Saturday, October 12. The featured Pokémon is Trapinch. This Community Day event will also take place a bit earlier in the day than in previous months. The event will happen on Saturday, October 12, from 11:00 a.m. to 2:00 p.m. local time. Trapinch will appear much more frequently in the wild during this time. Shiny Trapinch, Shiny Vibrava and Shiny Flygon will also make their Pokémon GO debuts.
If you evolve Vibrava (the evolved form of Trapinch) into Flygon during the event or up to one hour afterward, the Flygon will learn a move it can’t normally learn. Plus, during the event, Lure Modules will last for three hours and you’ll earn three times the XP for catching Pokémon! As a reminder, Shadow Pokémon cannot learn event-exclusive moves. Purify Shadow Pokémon featured on Community Day before evolving for them to learn the exclusive move. You do not need use a TM to change Return as a move from Purified Pokémon in order to learn exclusive moves. However, the exclusive move will replace Return, even if you have two Charged Attacks.
Source: Official Pokémon GO blog