If you’re used to getting up at O’Dark-thirty and going to bed sometime around 9:00 pm, you can switch your clock to 24-hour time.
Also commonly referred to as «wartime», this is where the day shift switches to 1200-2400, taking into account those nasty concerns about am/pm. And it’s easy to switch the phone. Just go to Settings > Date & Time and check «Use 24 hour format».