Like every nation, Greeks love to celebrate. Here is the list of national holidays:
January 1 (New Year's Day); January 6 (Epiphany); Clean Monday (Ash Monday/first day of Lent, or 41 days before Easter); March 25 (Feast of the Annunciation and Independence Day); Good Friday; Easter Sunday; Easter Monday; May 1 (Labor Day); Pentecost (50 days after Easter); August 15 (Assumption of the Holy Virgin); October 28 (Ochi Day); December 25-26 (Christmas Day and Boxing Day). Note: Greek Orthodox Easter occurs on May 5 in 2002.
Only on Greek Orthodox Easter and August 15 do you find that practically everything shuts down. You will have a harder time getting a room at the last minute on Easter and August 15 (especially the latter), and traveling requires stamina and downright pushiness, if you want to survive on the ferries and the highways. On the other hand, the local rituals and rites associated with these two celebrations are interesting and occasionally moving (the Epitafion procession on Good Friday), allowing you a glimpse into customs that date to pagan times.