-* `apt_updates` - the number of updates available on the system
-* `apt_security_updates` - the number of updates which are security updates
-* `apt_package_updates` - the package names that are available for update. On Facter 2.0 and newer this will be a list type, in earlier versions it is a comma delimitered string.
+* `apt_updates` --- the number of updates available on the system
+* `apt_security_updates` --- the number of updates which are security updates
+* `apt_package_updates` --- the package names that are available for update. In Facter 2.0 and later, this will be a list type; in earlier versions, it is a comma-delimited string.
+* `apt_update_last_success` --- The date in epochtime that `apt-get update` last ran successfully. This is determined by reading the mtime of the file `/var/lib/apt/periodic/update-success-stamp`. That file is generated by the `/etc/apt/apt.conf.d/15update-stamp` file.