Notes to Excel formula 

The shown all-time-formula claims 1369 charcters, but f.e. in ECXEL 2000-2003 the maximum of formula length was 1024.
I reduced it to 448 (less than 1/3), so it works also in Excel 5

=DATE(A1,4,MOD(A1%-11*MOD(A1,19)-DAY(A1%/4)-INT((A1%+46-DAY(A1%/25+1/3))/3),30)+MOD(2*MOD(INT(A1%),4)+2*DAY(MOD(A1,100)/4)-MOD(19*MOD(A1,19)+INT(A1%)-DAY(A1%/4)-INT((A1%+46-DAY(A1%/25+1/3))/3),30)-MOD(A1,4)+4,7)-7*DAY((MOD(A1,19)+11*MOD(19*MOD(A1,19)+INT(A1%)-DAY(A1%/4)-INT((A1%+46-DAY(A1%/25+1/3))/3),30)+22*MOD(2*MOD(INT(A1%),4)+2*DAY(MOD(A1,100)/4)-MOD(19*MOD(A1,19)+INT(A1%)-DAY(A1%/4)-DAY((A1%-11-DAY(A1%/25+1/3))/3),30)-MOD(A1,4),7))/451)-9)

Frank Schneider, Germany 85.199.76.237