Function            isdate - character classification

  Syntax              boolean isdate(int c);

  Prototype in        keyboard.h

  Remarks             determines if a character is valid for a date. Only
                      the following characters are allowed:

                           0  1  2  3  4  5  6  7  8  9  -  /

  Return value        returns true if c is a valid date character, FALSE
                      otherwise.