By default, a campaign has over fifteen types of entities enabled. If your world has no use of calendars or quests, these can be disabled.
While viewing your campaign, click on the
WORLD link in the campaign's sidebar, and then go to the
Modules subpage. From there, you can enable or disable types of entities that the campaign doesn't need.
Disabling an entity type doesn't delete the data from the campaign, it simply hides it. Only members of the campaign's admin role can enable or disable modules.