Select types of events that you want to see in your calendar:

Algorithm
SRMs
TopCoder Open
TopCoder Collegiate Challenge

Marathon
Marathon Matches

Design and Development
Design and Development contests posted

TopCoder High School
High School SRMs
TopCoder High School Tournament

Miscellaneous
TopCoder office holidays
Chat sessions in arena

New types
New types of events if they appear

Long events (> 24 hours) shown as:

Single continuous event
Two events: the start and the end

Link to your iCalendar:

http://topcoder-calendar.appspot.com/ical

Just import this URL to your calendar. For example,
add to Google Calendar
It might take some time before the calendar is indexed and displayed properly.

Any feedback is very welcome at mikhail.dvorkin@gmail.com.