YRBASE
tm->tm_year = ((int)(dosdatetime >> 25) & 0x7f) + (1980 - YRBASE);
yr = ((int)(dosdatetime >> 25) & 0x7f) + (1980 - YRBASE);
leap = ((yr + YRBASE - 1) / 4); /* leap year base factor */
if ((mo > 1) && ((yr+YRBASE)%4 == 0) && ((yr+YRBASE) != 2100))