Events

Events are either in-game or both in-game and real-world celebrations for special occasions. Events can last one day or several weeks and grant trainers a chance to complete their Pokédex by increasing the chance of acquiring rare or special Pokémon.

During them, there are various temporal changes to the game that can be applied (bonuses and perks for trainers) such as:
 * Specific Pokémon spawn increased.
 * Specific Pokémon in Eggs, Raid Battles and in temporary Research tasks.
 * Specific Pokémon wearing event-themed hats.
 * Extended duration of Star Piece, Lucky Egg, Lure Modules and Incense.
 * Increase of Incubator efficiency.
 * Reduced buddy distance and trading or evolving cost.
 * Multiplied Stardust, Candy and XP for several actions such as hatch, catch, transfer, evolving and battling.
 * Release of specific Pokémon species, forms and shiny forms.
 * Release of Special Research tasks.
 * Special shop offer.
 * Specific attacks.

Some events are worldwide available, while others can happen in a specific region. For instance, some events happened only on Europe, while others happened only on Japan.

Moreover, the events can be:
 * Unique events: events that happened only once.
 * Seasonal events: events that happened more than once. Normally, these events are related to holidays.
 * Other recurring events: events that happened more than once. Please go here for details.

2016
There were 5 in-game events in 2016. 4 of them were worldwide available and one was exclusive event for Japan.

2017
There were 20 events that occurred in 2017.

2018
There were 30 events during 2018.

2019
There were 34 events during 2019.

2020
So far there were 26 events during 2020.

Other events
These, following events unlike the rest aren't neither unique nor seasonal and they do not have specific year in which they happened.

Nest Migrations
Nest Migrations are the technical changes to the game in which Pokémon Nests changes species which spawns in the specific locations.

Community Day
Community Day is the first in game, regular event introduced in January, 2018. This event lasts only few-hours on one, particular day of each month and during it players can catch a Pokémon with an exclusive move that cannot be obtain normally in gameplay.

Safari Zone
Pokémon GO Safari Zone is a recurrent regional event, that happens in different locations around the globe. The events give Trainers the ability to catch region-exclusive Pokémon that do not usually appear in these regions.

Limited Research
Limited Research is a recurrent event that is hosted for a few hours and features exclusive Research tasks that may reward a Trainer with a shiny Pokémon.

Special Raid Challenge
Special Raid Challenge is a recurrent event that is hosted during a three-hour window and features a Pokémon as Raid Boss. This Pokémon may know one or more limited or legacy attacks and may also have a chance to be shiny. All Trainers will also receive up to five Raid Passes from Gyms at no cost.

Special Raid Event
Special Raid Event is a recurrent event that is hosted during a short period of time and features a returning Legendary Raid Boss which may have a chance to be shiny.

Legendary Raid Hour
Legendary Raid Hour is an occasional event that turns every available Gym to a specific Raid Boss during one hour. It usually occurs on Wednesday from 6 p.m. to 7 p.m. in local time zone.

Event Pokémon
Event Pokémon are Pokémon that wear clothing such at hats or scarves and can only be obtained during an special event. They cannot be mass-transferred, similar to Legendary, Mythical, or Shiny Pokémon. They usually do not appear in the Pokédex, because they are not handled as forms.