How to Match Sky Texture angle to Sun Lamp angle? (or the other way around)

I think this screen shot will explain best.

How can the sun lamp be matched to the angle of the sky texture, or the sky texture rotation matched to the angle of the sun lamp? If they don’t match they of course won’t look natural, but I’m not sure what the sky texture rotation translates to in terms of world coordinates.
Any help appreciated.

I think the sun position addon does that:

You set it to use Cycles’ sky and the sun lamp, select the geographical coordinates and the date and can then just simulate any time of the day: Cycles’ sky and the lamp will follow the settings in the addon.

IkariShinji, thank you once again! This add-on looks amazing! I’m about to give it a try.

Edit: Confirmed, it is amazing! Really, really useful.