According to Dale Arden, Flash has 14 hours to save the Earth in the 1980 film "Flash Gordon."
14 martian days x 24.623 earth hours in a martian day = 344.72 earth hours
The rotation period of Neptune is 16.1 earth hours.
A day on Jupiter is less than 10 Earth hours
Earth, Jupiter's days only last about 10 hours.
The Earth makes one rotation on its own axis every 24 hours.
The duration of Flash Gordon - serial - is 4.08 hours.
The duration of Flash Point - film - is 1.47 hours.
The duration of Royal Flash - film - is 1.7 hours.
The duration of Flash of Genius - film - is 1.98 hours.
The duration of Flash Gordon's Trip to Mars is 4.98 hours.
The duration of Flash Gordon Conquers the Universe is 3.67 hours.
3 hours 11 minutes according to Google Earth!
A flash flood
A flash flood.
according to google earth about 325 km or about 3 hours 29 minutes
Of course they will flash until the battery runs down. So the time depends on how good the battery is. I have personally seen them flash for 6 hours straight.
24 under normal circumstances but could change according to Einstien's special theory of relativity which is too complicated to get into here. Also, are you speaking of Earth hours, Lunar hours, Martian hours etc. Could change in relative proportions based on what you are comparing too. There will obviously be something other than 24 hours in 24 hours if you are comparing hours on Mars to hours on Earth. Please be more specific in your question.