Here Are the Tools You Need
The SunYou don't need a perfectly clear view of the sun, but since you will be measuring how high the sun is in the sky, you need to at least know where the sun is. A completely overcast day or if the sun is blocked by mountains won't really work.
The HorizonAgain, since you will be measuring from the horizon, you need to at least know where it is. This is hard to do if you are looking at say, a mountain range and are unsure exactly where the horizon is. Ideally, you'll have a clear view of the edge of the earth like over water or a field.
An Outstretched HandThis is your main tool and I'm guessing most of you have one of these handy (ha ha ha - OMG I'm so funny!).
How to Measure Sunset TimeImpress your friends and feel like a wilderness expert in just a few seconds!
Stretch Your Hand Out in Front of YouExtend your arm fully in front of you, palm facing in so your outstretched hand is bent at a right angle to your arm.
Line Up Your Pinky With the HorizonThe bottom of your pinky finger should align with the horizon.
Count How Many Fingers Between the Horizon and the SunMeasure how many finger widths to reach the sun, and count 15 minutes for each finger. Four fingers = 1 hour, 3 fingers = 45 minutes, you get it. If it's more than an hour before sunset, you'll need to use both hands.
That's it! The times are most accurate the closer you are to the equator, but it gives you a good approximation regardless. This is such a useful trick (life hack?? whatever that is exactly, but we'll throw that in for a little SEO) to use any time!