The place I worked at today has unique little feature. The back door faces mostly west to the setting sun. A few hours before the sun sets its light projects through the doors peep hole and puts a a round rainbow on a door. As the sun get lower the circle creeps up the door.

Today work was slow, so I taped up some paper up and tracked the circle as the sun went down. I marked the door roughly every 5 minutes. We now of a crude sundial on on the door. It covers from 3:55 local to 6:20. The trail go for close to 14 inches.

Because of the rainbow effect its kind of accurate. The width from the edge of red to the end of blue is just shy of the amount it moves in 5 minutes. So if red cross the mark its +1 minute, orange +2 minutes, etc. So for one, maybe two days its going to be accurate to the minute or so.

Since we now know the path I am going to try to make a better version. :)

Edit:
Here is an image of that suns Trail and the rainbow circle that i am following.
http://www.furaffinity.net/view/6631599/