Just don't try to use dates before January 1, 1900 (or 1904 on Mac). You can work with dates in Excel 1,000 years in the future, but if you try to do that for dates from the 1800s it will completely screw them up. I don't understand why this problem still exists today. If you work in a museum, or anywhere else where you deal with old dates, you have to constantly be on the lookout for this "gotcha."