If you can see the horizon and the sun you can estimate the time to sunset pretty accurately with this simple thumb rule type trick. Hold your hand out at arm’s length with your hand flat palm facing you and your fingers in line with the horizon. Place the edge of your hand on the lower edge (limb) of the sun and count the number of fingers between the sun and the horizon. Each finger is approximately 15 minutes before the sun sets. So if four fingers filled the space the sun will set in about an hour. Naturally people’s arms and fingers are different sizes so the 15 minutes per finger is an approximation, but it’s a very close approximation. This works best towards the end of the day when the sun is getting low in the sky, and if the horizon is the ocean rather than land the estimate is a lot more accurate.