As Mark said. Just click on "Fishing Times" (top left of every page). Then click on "Display Settings". Simple
I find the 24 hour easier. Don't have to worry about AM and PM. If you can count to 24 you are good to go. With AM / PM you have to first know if it is AM or PM and then count to 12...1800 hours or 6 o'clock ?? 1800 hours is 1800 hours. 6 o'clock could be 6 AM or 6 PM.
I know the 24 hour system is used by military for day to day work. But, for big boys with big toys type stuff, most military use Zulu time.
itsaboat mate...Life is just a boat and then ya marry one !