I experienced this on a flight from MAN to AUH with Etihad. The crew requested everyone lower their blinds shortly after take off (10:00am) the cabin was then really relaxing with the nice mood lighting.
We had no idea what was going on outside the aircraft or when the sun had set. I only realised it had gone dark outside when the exterior camera was just showing black, prompting me just to double check....
I did't feel tired until i knew the sun had set.