Notes and Domino now interprets any input in a date/time field as a date or time, no matter how obscure the format. You receive an "Invalid date format" error only when it is impossible for Notes to interpret a value (such as 99/99/99) as a date or time.
For example, when a date field is formatted to expect month, day, and year, and only one of the three variables is entered, Notes tries to guess what the other two entries are. If there is no month, then the default is the current month according to the operating system settings. If there is no day, the default is "01." If there is no year, the default is the current year. If an alphanumeric entry is made, Notes ignores the alphabetic characters and tries to determine the date based upon the numerals entered.