* No Fixed Rotation: Unlike Earth, which has a consistent rotation, comets don't have a fixed rotation period. They tumble and spin erratically as they orbit the Sun.
* No "Day" or "Night": Since a "day" is defined by the time it takes for a planet to rotate once, a comet doesn't have a clear day-night cycle. They are exposed to the Sun's light for varying lengths of time depending on their orbit and position.
* Varying Orbital Periods: The amount of time it takes a comet to orbit the Sun (a cometary "year") varies greatly. Some comets have short periods, while others take thousands of years.
So, to answer your question directly, there are no "hours in a day" on a comet because comets don't have days in the way we understand them.
