Final answer:
The time reveille and retreat are sounded on a military installation is set by the commanding officer or base commander.
Step-by-step explanation:
The time when reveille and retreat are sounded on a military installation is typically set by the commanding officer or the base commander. These military customs are part of the daily routine and serve as signals for the start and end of the day. Reveille is usually sounded in the morning to wake up the troops, while retreat is sounded in the evening to signal the end of the official duty day.