I don't know - most weeks I spend perhaps that amount outdoors (say 8/9 hours hillwalking at the weekend and 6 hours during the week gardening) and that is far more than most people I know.
However, that's in spring/summer/autumn and assuming the weather is OK. In December or January its entirely possible for me hardly to hardly see any sun at all due to short days (say 8am to 3pm) and poor weather - and if I am out I'll inevitably be covered in bad weather clothing.
Edit: I started taking Vitamin D a few years back and saw a dramatic improvement in some areas.
Edit2: Amusingly, I had no idea what Vitamin D was supposed to do when I started taking it, my wife had bought some and asked if I wanted some. It had a dramatic effect on anxiety levels that I was suffering from at the time - it was mid winter. The only side effect I noticed being truly bizarre and vivid dreams - again something that I didn't know about in advance but have read other people commenting on.
However, that's in spring/summer/autumn and assuming the weather is OK. In December or January its entirely possible for me hardly to hardly see any sun at all due to short days (say 8am to 3pm) and poor weather - and if I am out I'll inevitably be covered in bad weather clothing.
Edit: I started taking Vitamin D a few years back and saw a dramatic improvement in some areas.
Edit2: Amusingly, I had no idea what Vitamin D was supposed to do when I started taking it, my wife had bought some and asked if I wanted some. It had a dramatic effect on anxiety levels that I was suffering from at the time - it was mid winter. The only side effect I noticed being truly bizarre and vivid dreams - again something that I didn't know about in advance but have read other people commenting on.