This is regarding the: Internet Calendaring and Scheduling Core Object Specification (iCalendar)
Use VALARMs to set reminders ( 3.6.6, page 70)
A "VALARM" calendar component is a grouping of component properties that is a reminder or alarm for an event or a to-do. For example, it may be used to define a reminder for a pending event or an overdue to-do.
DESCRIPTION:This is an event reminder