An unusual timepiece can be found at the Petrovaradin Fortress of Novi Sad, Serbia. Locals often call it pijani sat (drunk clock), because its accuracy fluctuates depending on the season.

The clock consists of three interconnected systems: the timing mechanism that keeps time and powers the clock hands, a striking mechanism that sounds the quarter-hours, and another striking mechanism that sounds the full hours. The timing mechanism is sensitive to changes in temperature. When the weather is cold, the clock tends to run a few minutes behind; When it's hot, the clock tends to run a few minutes ahead.

Petrovaradin Fortress was built from 1692 to 1780, and the clock tower dates to around 1750. The baroque tower has black dials, one on each side of the tower. Its hands are the opposite of most clocks—the hour hand is longer while the minute hand is shorter. It was made like this so that sailors on the nearby Danube river could easily see the time from a distance. The numbers on the dial are Romans and their diameter is greater than two meters.

The army took care of the clock for almost two and a half centuries, but since 1952, the military fortification has been left to civilian management. It is still operated by hand and there's an employee who winds the clock every day. The top of the tower has a weather vane with a heart instead of a spear.