To prevent accidental or unauthorised changes to an event, they can be locked, and only changed once they are unlocked. Only an administrator or the user that locked an event can unlock it.
This feature is great to lock an event in place once its date and time is fixed and confirmed with a client or attending resources. Or to ensure its not accidentally changed without someone making a specific effort to unlock it first. All unlocking actions are recorded in the events activity log.
Events can be locked by clicking them in the schedule and choosing Lock
from the quick edit menu, or from the event settings menu from within an event.
Locked events show a small padlock icon in the popup details, and in the event if turned on in the view settings.