Match date from numeric date in Excel?

["cstrader232" <cstrader232@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

I want to match a numeric date variable from an Excel file to a numeric date 
value that AFL understands.
(has to be numeric to work in a loop)

My options in Excel seem to be:

Number of days since January 1, 1900

"julian" date in yyyy, num days since 1/1 format:
e.g. 2006153

But can either of these be matched to datetime()?

I don't want to have to use 3 separate numeric variables: M D Y

TIA