When creating an itinerary or quote in the builder you can choose to format the time in a 12-hour or 24-hour format setting. Here's how: 

You can get to the Trip Settings by clicking either on the name of the trip, or on the Settings button at the top of the screen.

Here's what each option means:
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​Trip Viewer's Default: This will show the time however your client's browser/phone/system is set.
​12 Hour (12:00 am - 11:45 pm): Will force the trip to always show as 12-hour
​24 Hour (00:00 - 24:00): Will force the trip to always show as 24-hour 

Please note, any trips created before 2/2/2018 will be set as 12-hour automatically but can be changed by following the steps above. 

Embeddable itineraries will always show 12-hour format unless that trip is set to force it to show 24-hour format.