The graph found over on Groovy Matter demonstrates how easy it is to estimate how long until sun down by using your digits and a bit of math.

cool.jpg

The trick involves extending your arm fully and count the number of finger widths between the sun and the horizon. Unless if you happen to have exceptionally chunky digits, each finger should count as 15 minutes, which means each hand width should be about an hour.

But remember, that this is just an estimate so if you want to get home before dark, add some extra time after you measure.