A great way to help you know how much daylight is left in a day if you are lost or stranded and in need of shelter before dark. Hold your hand out to the sun and make four fingers, now hold your hand directly under the sun and count the width until you reach the horizon. For each finger means there is 15minutes, so If you you find that there is only 2 hand widths between the sun and the horizon it means there is only 2 hours left until darkness falls. Remember this little tip and it might help you in a bad situation.
Zoomable image here : http://infothread.org/Survival/daylight%20estimate.gif