I'm sure you will agree that it's truly unrealistic to see the sun at 5 AM in the middle of December, and that's something we've thought about too. Winter months will see long nights of about 15 hours, and day time of about 9 hours, while summer months will see long days, meaning that your July nights will last about 15 hours, whereas the night time will only last 9 hours before the sun starts to rise again. This nifty little feature is sure to keep you immersed in the game world when you're going out drinking on Christmas Eve and it's dark at 6 PM in-game! This means that the sun will move very slowly across the sky in summer, and quickly in winter, too.
There are four times of day that are considered by the algorithm, which are each split into a certain number of hours. The hours of the morning are 6 AM until 11 AM, for example, and these times are what's considered "morning" by the environment system. What this means is you're far more likely to experience fog in the hours between 6 AM and 11 AM than you are between 6 PM and 9 PM, for example, and you're more likely to experience sun between the hours of 12 PM and 4 PM.
Server time is always Central European Time (plus European Daylight Saving Time if active)