Getting a date into the date selector

["Hobson, Neville" <ne...@mentorg.com>]

I use the BuildNumber task to set a new build number when I perform a
'tag' task on my svn repository. The build number is saved in the
build.number file.
I later create a zip file containing any files that have changed since
the tag was created - effectively a patch file.
The fileset that is used to create the zip uses a <date> selector, but
at present I have the date of the tag operation hardwired.
What I would like to be able to do is to set the date for the date
selector to the date of the last modification of the build.number file.
Any suggestions about how I might do this - or another way to get to the
same result?
 
Thank you,
 
Neville