Meaning a person of high rank or distinction is attested from c.1500 in English; as a longer way to say person, the word was in use from 1550s (but often slyly ironical, with suggestion that the subject is overly self-important).
If your system is standalone, the default sync interval for system time is 604800 seconds (7 days). If you are in a domain environment, the default sync interval is 3600 seconds (0.04166667 days). If you are using XP Pro, you can adjust your settings using Group Policy editor (GPedit - Administrative Templates\System\Windows Time Service\Time Providers) or you can adjust things through a registry edit (works for any version of XP).
If the earlier time could fall on one day and the later time on the next day, you may have to add 86,400 (the number of seconds in one day) to the later time, like so: Next we consider the case where your time data is defined as TIME(n). The usual way to take the difference of two times would be as follows: