When entering Greece, EU citizens are not required to carry their passports. An EU Identification Card provides adequate information. UK citizens need to carry a passport, but otherwise the entry conditions are the same as other EU nationals.
Citizens of the U.S., Canada, Japan, Australia, New Zealand, Israel, Norway, Switzerland, Iceland and several South American nations require only a valid passport to stay in Greece for up to 90 days without a visa. Nationals from a number of other countries are permitted to remain in Greece for 60 days without a visa. Visa extensions can be easily acquired by an application and payment of an extension fee to the proper authorities, while you must also be able to show bank documentation or other evidence which states that you have the means to support yourself without employment. Staying in the country with an expired visa is prohibited and subject to prosecution.
Lastly, Greek authorities prohibit entry to individuals whose passport states that they have visited the occupied region of Northern Cyprus after November 1983.
For more information , you may visit the Ministry of Foreign Affairs of Greece