Pokémon GO has announced today that they’re experimenting with a special event called Legendary Lunch Hour where, on March 13, 2019 from 12:00pm to 1:00pm in your local time zone, there will be an increased amount of raids available for that hour.
Although this is currently only confirmed for March 13, it sounds as though if there’s enough participation and a positive enough reaction, it will be something they may offer as a weekly event.