This module displays a last updated date line at the bottom of the browser window. It works by reading a variable which is set by some other means, usually a drush command triggered on cron.
The following is an example cron script which you can edit, save, make executable and periodically trigger from your user's crontab:
#!/bin/bash
cd /var/www/site_name
git pull origin master # Replace with the update command for your VCS
/usr/local/bin/drush vset -y staging_last_update `date +%s`
The following crontab entry will execute the cron script every 15 minutes.
*/15 * * * * sh /path/to/site_name.sh > /dev/null