How to control de data/time format

I've translated what the enduser will see for the Appointments + page. The dates are coming in the Month day, Year and the time is being shown as hh:mm AM/PM.

I would like to change to : day Month, Year and the time as hh:mm (24 hours format) like 14:00 instead of 2:00pm.

I've seen some info on the Shortcodes but it seems that was only to force the start date of weekly or monthy schedule using a certain format an not really to change how the data/time format is used on the generated pages.

thanks