tbng, have a look here,

http://j-walk.com/ss/excel/usertips/tip028.htm
--
Paul B
Always backup your data before trying something new
Please post any response to the newsgroups so others can benefit from it
Feedback on answers is always appreciated!
Using Excel 2002 & 2003


"tbng" <tbng@discussions.microsoft.com> wrote in message
news:9219070E-F5BD-4E03-93D5-3A2801EAC1F7@microsoft.com...
> As an historian, I must calculate dates prior to 1900, but Excel 2000 only
> permits pre-defined calculations from January 1, 1900 and later. How do I
> calculate the days between October 10, 1836 and December 14, 1917?