The easiest thing for you would probably be to have them enter the date in a date picker and then the time separately. You have two opotions for the time:
1) Create a text field with a custom pattern that validates the way they enter data. You could create a default time in the format you want them to use.
2) Create drop down lists for the hours and minutes. The user selects those and then you can use JavaScript to store the values in whatever format you want.
Hope this helps!