The contest is held on the first full weekend of August, beginning at 1800 UTC Saturday and ending at 1800 UTC Sunday. http://www.arrl.org/222-mhz-and-up-distance-contest

Third full weekend of August and September. Operations may take place for 24 hours total on each contest weekend. Each weekend begins at 6:00 AM local Saturday though 12:00 midnight local Sunday. http://www.arrl.org/10-ghz-up

http://ncjweb.com/naqp/

The third Sunday of April, August and December from 1800 UTC through 2359 UTC. http://www.arrl.org/rookie-roundup

The second full weekend of September. Begins 1800 UTC Saturday and runs through 0259 UTC Monday. http://www.arrl.org/september-vhf