Function            date_convert - convert date formats

  Syntax              boolean date_convert(void *source, void *dest,
                                           int stype, int dtype);

  Prototype in        dateadv.h

  Remarks             date_convert will convert a date from virtually any
                      date format to any other. The parameters *source
                      and *dest must be pointers pointing to a piece of
                      memory allocated as the proper data type. stype and
                      dtype determine the format of source and dest.

                      Due to the great number of formats supported, a
                      chart of valid date formats is provided in Appendix
                      B.

                      Limited error checking is done on passed data. If
                      an invalid date format is passed, unpredictable
                      results will occur.

  Return value        returns TRUE is the conversion was successful and
                      FALSE if the date could not be converted.

  Note                This function does NO function calls except for
                      isleapyear(). I've tried to optimize this function
                      as much as possible for speed, not size. If you
                      only need to convert between, say, Calendar and
                      Julian dates, you may be better off using the
                      functions listed in datehk.h.

  See also            Appendix A, B
                      Cal...(), ddatetofull(), ddatetoshort(),
                      ddatetostr(), fulltoddate(), Greg...(), Jul...(),
                      monthexpand(), shorttoddate(), strtoddate()

  Example             see demoadv.c