Minecraft wiki entry for Tick, associated text: A gametick is where Minecraft's game loop runs once. The game normally runs at a fixed rate of 20 ticks per second, so one tick happens every 0.05 seconds (50 milliseconds, or five hundredths of a second), making an in-game day last exactly 24000 ticks, or 20 minutes. However, if the computer is unable to keep up with this speed, there are fewer game ticks per second (TPS). As the vast majority of actions are timed based on tick count rather than on wall clock time, this means that many things take longer on a slower computer.