Maybe Excel doesn't support dates earlier than 1900... have you googled it?
EDIT ==============
I googled it, and found out that the earliest possible date Excel will accept is 01/01/1900. You're out of luck, Sparky. Here's the link I found the info at:
http://www.ozgrid.com/Excel/free-training/excel-lesson-13-basic.htm[
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Scroll down to the section labeled "Excel Dates and Times".