The Categories box on the left sidebar of the home page lets you filter the calendar view to only show events that belong to the categories you select. Some categories may be unselected by default, but the system will remember your most recently selected categories during a session.
Check the box next to a category to show matching events on the calendar. Uncheck a category to hide those events. An event that participates in more than one category will display if any of its categories are selected in the filter.
You can check or uncheck all the categories at once using the circled check icon in the header, to the right of the word Categories.
Categories marked with an arrow pointer have sub-categories you can show or hide by clicking the arrow. Checking or unchecking a parent category will check or uncheck all of its sub-categories. You can also individually check or uncheck sub-categories.