You can either choose the datepicker to have a "long" date, even only "time" or you can create your custom date.
I always use this format, as it's the most easy one to understand for users (IMHO): yyyy.MM.dd HH:mm
This can be done in the designer the fastest, just change the property.
Or, change it in the program with
YourDatePicker.Format = DateTimePickerFormat.Custom;
YourDatePicker.CustomFormat = "yyyy.MM.dd HH:mm";