A sundial is the first ever device that can tell time and it was created some 4000 years ago by the Egyptians and was a crucial invention of that time. Sundials work by simply casting the suns shadow on a pre-set surface which has markings on it that show the precise time. The first ever sundial or sun clock as it is also called was a device that had a straight stick pointing towards the sky and it was able to tell time but not quite accurately enough. When Egyptians started to standardize the days length and divided it into 12 hours then more accurate sun dials were made that had a triangle shape where the top point was pointing towards the North pole and at the opposite side the half circle was divided into 12 distinct parts that we now know as hours.
Imagine a time when you did not know what was the accurate time and you had to rely on the movement of the sun to predict when the evening will come. That must have been a very frustrating time because no one could be sure how much time is left till some particular date or time. And if measuring days would have been simple enough that people could have created a sense of what is the time then counting days and seasons would have been a much much harder task. Imagine what would happen if we did not know how to tell time to the present day. Every meeting should have to be scheduled only approximately any appointments would be pointless and we would have to go to sleep as well as eat only when out bodies would tell us to do that. People lived like this for thousands of years and survived but with the advent of mechanisms like this sundial we started to set appointments and predict when what would happen.
A sundial was a great invention but it had its flaws because you had to make it stationary and it would show the time only when the Sun was shining and that is why there were only 12 hours not 24 hours on that clock. And also when the day was cloudy people again had no means of telling the time so you can imagine what would happen if everyone would rely on a clock like this but then a storm comes and every time telling device disappears. That is why people started to look for alternative methods of telling time and first they used the same materials to create a portable sundial but it did not work as well as you would like but later on some other methods proved to be useful.
Till this day we can find various sundials around the world that are made as an art form or simply as a tourist attraction and these sundials can tell time accurately enough within 5 minutes and that is a great achievement knowing that these things were invented 4000 years before we were born.