In lot of cases users will want to have their own format of the Date, Time or DateTime field. 

This field uses the Bootstrap DateTime Picker https://eonasdan.github.io/bootstrap-datetimepicker/


So, in order to edit the format you will need to go in "public/assets/js/demo.js" on line  60. 

There you will find all the settings for the datetime fields


$('.datepicker').datetimepicker({
            format: 'MM/DD/YYYY',
            icons: {
                time: "fa fa-clock-o",
                date: "fa fa-calendar",
                up: "fa fa-chevron-up",
                down: "fa fa-chevron-down",
                previous: 'fa fa-chevron-left',
                next: 'fa fa-chevron-right',
                today: 'fa fa-screenshot',
                clear: 'fa fa-trash',
                close: 'fa fa-remove',
                inline: true
            }
         });

         $('.timepicker').datetimepicker({
//          format: 'H:mm',    // use this format if you want the 24hours timepicker
            format: 'h:mm A',    //use this format if you want the 12hours timpiecker with AM/PM toggle
            icons: {
                time: "fa fa-clock-o",
                date: "fa fa-calendar",
                up: "fa fa-chevron-up",
                down: "fa fa-chevron-down",
                previous: 'fa fa-chevron-left',
                next: 'fa fa-chevron-right',
                today: 'fa fa-screenshot',
                clear: 'fa fa-trash',
                close: 'fa fa-remove',
                inline: true

            }
         });