The Base Event object "understands" time / date and works with the Calendar Object Type. As a basic objet type it is usually "inherited" by objects, so that they show on the Calendar.
The Base Event object type is usually used as an inherited object type, giving the principal object type access to the calendar and time realted functions. For example, if you want an object type you are creating for your bespoke service to display in a Calendar, you would build your object / properties to suit your system - then inherit the Base Event object type. This will give your new Object Type access to the following propoerties, which are built to coordinate with a Calendar object type.