Here's a challenge: right now, try to estimate what time the sun will set this evening within a 15-minute window. Unless you've been paying close attention to previous sunset times, you've been studying an almanac recently, or you cheated and Googled it, you'll probably have a hard time estimating sunset time that accurately.

Well…. actually, that's not necessarily true. There is another way to estimate remaining daylight hours, and it's much more practical than any of the other methods we mentioned above.

This extremely simple trick uses nothing more than your fingers and the horizon, and it takes mere seconds to do. It's one of those skills that everyone should know about, even if you're not a prepper or survivalist. It's just a handy life skill in general (forgive us).

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Here's an illustration of how it's done, via an infographic we found through LifeHacker.

Simply extend your arm, and align the top of your index finger with the bottom of the sun. Each finger width between the sun and the horizon should provide about 15 minutes of daylight. This lets you figure out how long you have to make camp or gather firewood before sunset.

Of course, like the infographic above mentions, there are a few drawbacks:

• It's not 100% accurate, hence our use of the word “estimate”. If you have short and stubby T-rex arms, your readings may be thrown off a bit.
• The accuracy diminishes the closer you get to the north or south pole, since the sun's movement will appear to slow as it nears the horizon. Then again, some polar regions have sunlight for almost 24 hours each day, so you may not have to worry about sunset at all.
• The accuracy also diminishes the closer you get to the tropics, but in the opposite direction. Near the equator, the sun will set faster than you might estimate using this method.
• Obstructions near the horizon, such as low-lying clouds, can cause daylight to disappear faster than you might expect.
• Some residual light will persist as the sun begins to sink behind the horizon.

To improve the accuracy of this method, get out there and try to estimate the remaining daylight where you live. After using this trick a few times, and paying attention to a wristwatch, you'll be able to figure out more accurately how many minutes of light each finger represents in your region.

Written by Patrick McCarthy