I think it's just the time zone you start the sim from not updating until a restart. If you look at many actual patrol reports, the time is followed by a letter that indicates what time zone is in effect.
http://www.geocities.com/Pentagon/1592/nautilus1.htm
http://aa.usno.navy.mil/faq/docs/world_tzones.php
The clocks were reset when the zone changed and SH4 doesn't go there.
Buddahaid