For your information, a list of Public holidays in Greece during 2012. Some of these are ‘floating’ holidays, such as Greek Orthodox Easter and others, such as the 25th of March and 28th of October are fixed. There are other religious holidays throughout the year which I have not noted but you can find out more from: The Greek Orthodox Archdiocese of America.

Part of the Epiphany service in Porto Heli, 06/01/2010.
January 2012: 01-New Years Day/Protichronia, 06-Epiphany/Ton Foton, 30-Three Holy Heirachs/Trion Iearachon(celebrated only in the schools)
February 2012: 27-Clean Monday/Kathara Defthera (start of Lent)
March 2012: 25-Independence Day/Tou Evagelismou
April 2012: 13-Greek Orthodox Good Friday/Megali Pareskevi, 15-Greek Orthodox Easter Sunday/Kiriaki tou Pascha, 16-Greek Orthodox Easter Monday/Deftera tou Pascha
May 2012: 01-May Day/Labour Day/Protimayia
June 2012: 04-Holy Spirit Monday/Greek Orthodox Whit Monday/Kataklysmos
August 2012: 15-Assumption of the Virgin Mary/Kimisi tis Theoutokou
October 2012: 28-’Ochi’ Day/Epetios tou Ochi
November 2012: 17-Aniversary of the University uprisings/Polytechniou (Schools celebrate only)
December 2012: 25th-Christmas Day/Xristouyena, 26-Boxing Day/Synaxis Theotokou
If you are wondering about local high days and holidays, see my post on Local holidays, my Notice Board and keep an eye on my Events category which will contain the latest updates.