At times, I cannot recall the time commands for find for BSD unix.

find files modified within the last day

find ./ -Btime -1d

find files accessed within the last day

find ./ -atime -1d

find files created within the last day

find ./ -ctime -1d

find files modified between 50 and 100 days ago

find ./ -Btime +50d -Btime -100d

Perl

Try the handy find2perl utility that comes with perl and uses the File::Find package. It writes a little script for you that you can adapt. See the perldoc site for further details.

An example from the documentation

find2perl / -name .nfs\* -mtime +7 \
-exec rm -f {} \; -o -fstype nfs -prune

Gives you a wanted subroutine like so:

sub wanted {
  /^\.nfs.*\z/s &&
  (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_)) &&
  int(-M _) > 7 &&
  unlink($_)
  ||
  ($nlink || (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_))) &&
  $dev < 0 &&
  ($File::Find::prune = 1);
}

Here’s a modification that gives you files ending in txt modified between 50 and 20 days ago.

sub wanted {
  my ($dev,$ino,$mode,$nlink,$uid,$gid);

  /\.txt\z/s &&
  (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
  (int(-M _) < 50) && (int(-M _) > 20)
  && print("$name\n");
}