In rare cases you may need to back up files older than a given date. You can do this by placing an exclamation point (!) immediately before the date. The exclamation point reverses the sense of the search. For example,
bru -c -n !10-Jan-92
will back up all files older than January 10th, 1992. Be aware that you may have to use your shell’s escape character to use the ! on the command line.