+On systems where the boot time is available, B<sudo> will also not
+honor time stamps from before the machine booted.
+
+Since time stamp files live in the file system, they can outlive a
+user's login session. As a result, a user may be able to login,
+run a command with B<sudo> after authenticating, logout, login
+again, and run B<sudo> without authenticating so long as the time
+stamp file's modification time is within C<@timeout@> minutes (or
+whatever the timeout is set to in I<sudoers>). When the I<tty_tickets>
+option is enabled in I<sudoers>, the time stamp has per-tty granularity
+but still may outlive the user's session. On Linux systems where
+the devpts filesystem is used, Solaris systems with the devices
+filesystem, as well as other systems that utilize a devfs filesystem
+that monotonically increase the inode number of devices as they are
+created (such as Mac OS X), B<sudo> is able to determine when a
+tty-based time stamp file is stale and will ignore it. Administrators
+should not rely on this feature as it is not universally available.
+