Last night I drank the last three pints of a brew that was bottled 5 months ago. They were stored on the floor of a spare bedroom which has an East facing window. They were in the open for 3 weeks then moved to the corner in the "shade" of my computer desk. One was in a dark brown swing top bottle and the other two were in clear glass bottles.
The dark bottle beer was the original pale colour and the taste was fresh. The other two were noticably darker and did not taste as good.
In future I shall use dark bottles where I can and cover the bottles to protect from light. I personally am surprised at the magnitude of the effect of light.