The presidential guards are special unit which are dedicated to guard the Greek Parliament and the Monumnet of the Unknown Soldier. 24 hours a day and 7 days a week. In fact, each couple of guards keep their post for 1 hour. Furthermore, in that hour, the Evzones must stand still without moving. Even more, they must not move their face or make expressions! Each 1 hour the guards change with a special ceremony procedure!