How does time pass in Euro Truck Simulator 2?

Question 1: How exactly does time pass in ETS2?

Sleeping

If you go to your garage (usually at certain gas stations too), you can stop your engine and sleep for around half a day. However, you can only do it 3 times at once before it removes the option for a little while.

Switching Trucks

If you have 3 trucks and 2 other drivers, go into the Truck Manager screen and keep switching trucks with the other drivers. When you switch, it should say "It'll take X hours to switch to this truck." or something similar. Keep doing this until both the trucks are "Idle" or enough time has passed.

Playing the Game

Pretty simple. Just go around doing jobs and driving around.

Question 2: Does the method how it passes affect delivery offers too?

Yes, anything that makes time pass affects delivery offers.

Question 3: Does it pass when you are chilling in the menu?

No, the menus pause the game completely.

Hope this helped.

tl;dr: driving makes time pass 5x compared (30sec) to standing still(2.5min).

I timed it at multiple speeds, seems 10 minutes game time takes two and a half minutes real time at standstill, if you are driving 10 minutes game time passes in just 30 seconds, 5 times as fast. don't know if it slows further if you stand still for longer. Or exactly what happens if you drive in a very tight circle, at first it seemed the 30 seconds later 2.5 minutes

Seems to me that time is NOT passing when you are stationary on the street (es. At traffic light, or just idle in the street). That time pass very slow when you are on urban street, and faster on the highway. I guess, but not sure, that time passing is connected with your speed.