I figured this one out by using the
ant manual.
Under "Concepts and Types" I found
Selectors.
Core Selectors
Core selectors are the ones that come standard with Ant. They can be used within a fileset and can be contained within Selector Containers.
The core selectors are:
<contains> - Select files that contain a particular text string
<date> - Select files that have been modified either before or after a particular date and time
<depend> - Select files that have been modified more recently than equivalent files elsewhere
<depth> - Select files that appear so many directories down in a directory tree
<different> - Select files that are different from those elsewhere
<filename> - Select files whose name matches a particular pattern. Equivalent to the include and exclude elements of a patternset.
<present> - Select files that either do or do not exist in some other location
<containsregexp> - Select files that match a regular expression
<size> - Select files that are larger or smaller than a particular number of bytes.
<type> - Select files that are either regular files or directories.
<modified> - Select files if the return value of the configured algorithm is different from that stored in a cache.
Come on back with questions if you need help getting the <date> selector to work.