A mission timer is a device that is used to keep track of time in a mission. There are several synonyms for the word mission timer which are used interchangeably in different contexts. Some of the commonly used synonyms are countdown timer, event timer, task timer, performance timer, and action timer. Countdown timer is often used to indicate the time remaining for a particular event or activity to begin. Event timer and task timer are used when the mission has specific tasks or events that are scheduled to occur at different times. Performance timer is used to measure and record performance metrics during a mission. Finally, an action timer is used to track the duration of an action or sequence of actions.