When you are outdoors or living with limited (or no) electricity, tasks are measured by how much daylight remains. Light from the sun is necessary in order to accomplish many duties. Knowing how much natural light remains in the day will tell you how to set your priorities regarding things such as shelter and fire.
This is important, especially if you are accustomed to a routine that includes things like a late evening meal with time to relax afterwards. The preparation and cleanup will best be done while the sun is still shining and you are able to see what you are doing. It is NO FUN to wake up the next day to soiled cookware because there wasn’t enough light to do the job right the night before. Ask anyone that has tried to set up a shelter in the dark, and you will quickly hear enough stories to make you want to avoid that scenario also.
To estimate how much daylight remains, locate the sun in the sky without looking directly at it. Fully extend your arm and turn your hand to look at your palm with your fingers pointing to the side. Measure how many finger-widths of space there are between the bottom edge of the sun and the horizon line. For every width of a finger you can place between the sun and the horizon, there is approximately 15 more minutes of daylight. So, if you had a single span of your hand between the sun and the horizon, there is about an hour (4 fingers X 15 minutes) before sunset.
In the morning hours this method can be used to estimate how much time has passed since sunrise. Additionally, measuring the distance of the sun from both the eastern and western horizons, will give you a good general idea of the length of time you will between have sunrise and sunset. Half of that time will give you the hours between sunrise/sunset and mid-day. This valuable tool will help you avoid becoming so consumed with any single task that you run out of time to accomplish other important things.