The UDF should return a number to the cell, which can be formatted as
a date to suit your requirements. The number is an integer measuring
the number of elapsed days, with 1st Jan 1900 = Day 1. Excel assumes
(incorrectly) that 1900 was a leap year, so you need to take this into
account. The serial value for today's date (17th Jan 2008) is 39464.

Hope this helps.

Pete

On Jan 17, 11:31*pm, ep wrote:
Hi all,

I have a c# udf accessed as an automation add-in that needs to return dates
to Excel. I know I can't manipulate the cell's NumberFormat from within the
UDF, but is there a way to return a value that will be formatted in Excel as
a date? It seems any string value I return will default to general. Let me
know if any other info would help.

thanks