Customizing the display options of your form fields can be completed in your control panel. If you wish to edit the display of your time field, you can do so by clicking on the form icon at the top of your control panel.
Click on the option for form editor and then choose your form by clicking on the form name.
You can modify your display options for your time field by clicking on the pencil icon to the right of the field.
Choose the option for advanced from the drop down menu.
You can modify your display options for your time field by choosing the two options listed: 12 Hour or 24 Hour.
Make sure you choose save changes to update your choice.