Why is my OLE data source data not querying consistently?

I have a Microsoft Excel 2003 file that I am querying from C# 2.0 using an OleDbCo开发者_StackOverflownnection.

One of the cells in the Excel file is formated as a short date and displays in Excel as "1/1/2009". If I change the format to General the text displayed in that cell changes to "39814".

If I query the Excel file while the file is open, I receive "39814" in the result set.

If I query the Excel file while the file is closed, I receive "1/1/2009" in the result set.

Why the inconsistency with importing data from this Ole Data Source?

Thank you,

Keith