A event normally refer to either Seasonal either Seasonal Event (SE) or Great Construction Era (GCE).
Seasonal Event[]
Seasonal Events are held every season. However there are two exceptions due to the incident between developers and publishers. Seasonal Event refers to (normally 4-5) clearing missions
Main page: Events/Seasonal_Events
Great Construction Era[]
Great Construction Eras are usually held between seasonal events. Rather than a mission, GCE is a special offer, probability of getting ships would be doubled to encourage admirals spending their resources and having fun (sometimes it is not fun at all)
Main page: Events/Great_Construction_Era
Time-limited Quests[]
Before a event, usually there are some time-limited quests to help admirals to prepare for the event. There are some festival-related quests, they are also time-limited.
Main page:Events/Quests