It appears that you cannot enter a date from the keyboard if the current value is null and max Date is set to a date in the past. Moreover, you also cannot enter a date from the keyboard if the max date is the current date. To verify, use the following declaration in the JSFiddle examples on the API page (an excellent new feature on the web page, btw):
$("#jqxDateTimeInput").jqxDateTimeInput({
width: '175px',
height: '20px',
theme: 'energyblue',
formatString: 'MM/dd/yyyy',
value: null,
maxDate: new Date()
});
If you replace new Date() with new Date(tomorrow) you will be able to enter a date from the keyboard.
A work-around to get the current date to work is to set the max date to 23:59:59.999 on the current date.