Thinking of "fourteen hundred hours" as 2 o'clock will take some getting used to, but there's one really good reason to switch your cell phone to military time: You'll never make an afternoon alarm mistake ever again.
Have you ever woken up late one morning to find your 6 a.m. cell phone alarm was actually set to go off at 6 p.m. that night? It's an easy (and far too common) mistake to make. Luckily, a quick switch of your phone's settings to military time will make the problem go away for good.
The reason airlines, public transit and the armed forces use 24-hour "military" time is to avoid confusion between a.m. and p.m. hours. You can take the same approach with your cell phone's clock settings to avoid accidentally setting your morning alarm at an afternoon hour.
After you make the switch, the time of day displayed in the morning until 12:59 in the afternoon will look the same, but the afternoon hours will switch to display 13:00 (for 1 p.m.) until 23:59 (for the minute before midnight). So when you set an alarm for 6:30, you'll know it'll go off in the morning to get you up and ready on time.
Not on board with a full switch to military time? Here's another tip:
If you want to be able to set alarms in 24-hour time, but keep your smartphone's main clock in the more familiar 12-hour time, install a secondary alarm clock app (like this one for iPhones). You can switch the app's alarm setings to military time, but keep your phone's main clock the same.
(Images: Composite Image [1,2,3], personal iPhone screenshots)