Event Announcement:

“Trainers,

We are excited to announce that Giratina has reemerged from the Distortion World and returned to raids!

Date + Time

From Monday, September 23, 2019, at 1 p.m. PDT (GMT −7) to Thursday, October 17, 2019, at 1 p.m. PDT (GMT −7): Giratina in its Altered Forme will be available in five-star raids.

On September 25, 2019, from 6:00 p.m. to 7:00 p.m. in your local time zone: There will be an increased number of five-star raids, featuring Altered Forme Giratina.

Features

If you’re lucky, you might encounter a Shiny Altered Forme Giratina!

Start prepping your teams to take on this Ghost- and Dragon-type Legendary Pokémon. There are still many mysteries to be unraveled about the Renegade Pokémon! Stay safe, and happy raiding!

—The Pokémon GO team”

Source: https://pokemongolive.com/en/post/shinyalteredformegiratina2019/