Niantic has announced that a Limited Timed Research featuring Marill will be held on Sunday, May 9th, 2021, from 8:00 a.m. to 10:00 p.m. local time.

May Limited Research featuring Marill is coming soon!

Trainers, As Fairy-type Pokémon continue to appear more often in the wild during the Luminous Legends X event, you can look forward to a Limited Research event featuring the Water- and Fairy-type Pokémon Marill!

On Sunday, May 9, 2021, from 8:00 a.m. to 10:00 p.m. local time, you can complete event-exclusive Timed Research tasks that lead to encounters with Marill. If you’re lucky, you might even encounter a Shiny Marill! You’ll also be able to complete event-exclusive Field Research tasks that lead to encounters with Marill.

Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change.

Source: https://pokemongolive.com/post/limitedresearch-may2021/?hl=en