New Year's Day, New Year's Eve, Epiphany, Green Monday, Greek Independence Day, Greek Cypriot National Day, Greek Orthodox Good Friday, Greek Orthodox, Easter Monday, Labour Day, Pentecost, Assumption, Boxing Day, Christmas Eve., Christmas Day, Cyprus Independence Day, Greek OHI Day, etc.
That will vary depending on the religion.
Yes, people can and do celebrate Christmas for non religious reasons. Though Christians celebrate it for the birth Christ, Christmas has become very secular. Many celebrate Christmas without connecting it to the birth of Jesus.