Here is the test I ran :-
[AS]
Real Nav Auto Fix timed GMT
[DESCRIPTION]
test fix by GMT
[DESCRIPTION_END]
[CATEGORY]
Real Navigation
[SUBCATEGORY]
Position on patrol
[COMMANDS]
Report_position_celestial,0,0,0,0,0,0,0
Wait_for_time,12,00,0,Noon Fix,0,0,0;(1200GMT)
Report_position_celestial,0,0,0,0,0,0,0
Wait_for_time,19,00,0,Post Meridian Fix,0,0,0;(1900GMT)
Report_position_celestial,0,0,0,0,0,0,0
Wait_for_time,00,00,0,Post Sunset Fix,0,0,0;(0000GMT)
Report_position_celestial,0,0,0,0,0,0,0
Wait_for_time,05,00,0,Pre-dawn Fix,0,0,0;(0500GMT)
Report_position_celestial,0,0,0,0,0,0,0
Wait_for_time,07,00,0,Ante Meridian Fix,0,0,0;(0700GMT)
Report_position_celestial,0,0,0,0,0,0,0
Loop,-1,0,0,0,0,0,0
[COMMANDS_END]
Worked very well
Using GMT to avoid missing a fix if crossing a time zone means-
To get nav officer to call noon fix it must be noon local time.
most of the game is played :-
GMT 0 +/- 3

how to offset
Also does anyone have suggestions as to the correct time to hit sunset etc during North/South and seasonal changes