Just checked the website and found the sun still out. Looked at my window (view over swindon) and found it dark and wet.

How long is the day in CVO in the winter

Take a look here It gives the times over the year. In the climate statistics.

We were out in December and found that Portugal was about an hour behind the UK for sunset, ie started to loose the daylight about 5.15/5.20pm. Also meant though that sunrise was later than UK by about the same amount..

I think you'll find the sunrise is earlier than the UK as well Lesley. All to do with being closer to the equator. It will start to go the other way now we are past the winter solstice.

Talking of which, the cave at Algar Seco has a ridge cut out in the wall that seems to point towards the setting sun. Is that its purpose?

sorry, mind you I don't usually get up so early in Portugal than I do in the UK, it just seemed darker in the morning to me, must have been the wine from the night before....