What tag or variable is used to derive the files that were added today, yesterday, this week, last week, this month, etc.? I'm asking because I'm trying to be more specific: say, for instance, find all files that were added just 3 weeks ago, or even just 24 days ago. Thanks!
If you refer to the Collections with these names, IMatch produces them from the file history. See the documentation of the History Panel in the help.
For your purpose, see also the the File.* variables in the help, like
{File.Added}
{File.Updated}
{File.Modified}
{File.Created}