#!/bin/bash

if [ -z "$1" ] ; then
   echo "usage $0: <number of days>"
   echo "   returns the date it was N days ago expressed as seconds since 1969"
   echo ""
   echo "example: dar -c backup -af -A \`$0 3\` <other options to dar...>"
   echo "   \"backup\" will only contain files that have changed during the"
   echo "   last 3 days"
   exit 1
fi

echo $(( `date +%s` - $1 * 86400 ))