When you are out in the wilderness it can be important to know how many minutes of light are left in the day. You might need to know how long you have to make a fire or shelter. The following Survival Tip can probably be accredited to many sources, but I forget where I saw it. I could have seen it on Survivor Man, Man versus Wild, or read it online.
When the sun is nearing the horizon, stretch your arm as far out in front of you as possible, with your fingers extended. Your thumb should be pointing upward. The distance between each fingers is roughly 15 minutes of time until the sun sets.
Depending on where the sun lines up with your fingers, you should be able to gauge how much daylight is left. Although I have not yet tried it, you could probably use two hands to gauge up to an hour and a half before the sun sets. Try this out, or at least file it in the back of your brain under the just in case scenario.