This is done by either using the:
Param1 values (Normally used for gamelength)
or
Param2 values (Normally used for Score limit)
In your editor setup, change your map time to 0:00 hrs (midnight)
and then the skiptime values will be around about correct for the sunrise and sunset timings depending on time of year you selected
(Tweak the values until you get the results you are after
Skiptime simply advances time from the actual daytime setting
One thing to note
To reset param1 back to say a 30 minute game, then you need to re-declare its value after it has run through the "Skiptime" lines
eg Param1 = 1800, resets the value to 30 minutes (1800 is the number of seconds)
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Description.EXT entries
titleParam1 = "DAYTIME";
valuesParam1[] = {1,2,3,4};
defValueParam1 = 1;
textsParam1[] = {"Dawn", "Midday", "Dusk", "Night"};
Init.sqs Entries
?(param1 == 1):skiptime 6.2
?(param1 == 2):skiptime 12
?(param1 == 3):skiptime 18.4
?(param1 == 4):skiptime 0.1
Param1 = 1800