October 31- November 1 Samhain: a sabbat
November 21- November 22 Musemass
December 20- December 21 Yule: a sabbat
December 24- December 25 Modranect
January 15- January 16 Skillfest
January 31- February 1 Candlemas: a sabbat
February 28- March 1 Hearthday
March 20- March 21 Ostara: a sabbat
March 31- April 1 Vertmass
April 30- May 1 Beltane: a sabbat
May 29- May 30 Memory Day
June 23- June 24 Midsummer: a sabbat
July 19- July 20 Sunfest
July 31- August 1 Lammas: a sabbat
August 12- August 13 Diana's Day
August 24- August 25 Day of the Tides
September 20- September 21 Mabon: a sabbat
October 11- October 12 Eldmas
Only the Sabbats are celebrated by all Wiccans. Wicca is a individualist religion. Therefor witches or even covens can hold rituals and celebrations when they want. We don't like more then thirty days to pass before we perform a ceremony. It keeps us in touch with our faith. Most witchs do there magickal work on the New or Full moon.
You will notice that on all the sabbats, there are listed two days. In the old religion, a sabbat celebration lasted from sunset to sunset.