The most ancient ways of measuring time were known for 2000 years B.C. and their development continued until the first centuries of the new time. Timekeeping instruments of that period are sometimes called the simplest, and their era ends with the first important improvements in mechanical watches with wheeled transmission. This includes many types of sundial, water, fire, sand and other watches, which have played an important role in the history of timekeeping as well.
Undoubtedly, the most important and the most common timekeeping device was a sundial - the only one of the listed types of watch based on the apparent daily and sometimes annual movement of the Sun. Occurrence of these clocks is connected with the moment when the person realised interrelation between length and position of a solar shade from those or other subjects and position of the Sun in the sky. Exact date of occurrence of sundial which in the original form had the form of an obelisk, is unknown. Some historical sources believe that the first mention of the sundial was made in the manuscript of the Chinese Chiu-Pi of the period around 1100 BC, which states that with the help of sundial, the Chinese easily set the summer height of the sun at 79°06'20", and the winter - at 30°22'20", and from here they determined the inclination of the ecliptic at 23°52'. The oldest surviving written records of the sundial, dated 732 BC, are found in the Bible, in the twentieth chapter of the Book of Kingdoms. The sundial Aha-za here is understood to be the obelisk sundial of King Ahaz, who lived about 732 BC. The discovery of the ancient Egyptian sundial of the 13th and 15th centuries BC indicates that the actual period of appearance of the sundial was much earlier than it follows from the known until now written monuments.
The Gnomon, a vertical obelisk with a scale on the ground, was the first sundial to measure time by the length of the cast shadow. The fact that these obelisks were used by the Egyptians to worship the cult of the Sun god at the same time is confirmed by the records of the ancient writers Aristophanes, Athenios, Evbol and others. These sacred obelisks usually stood in front of the temple entrances. The role of gnomons was also performed by direct pylons in public squares and markets. The first obelisks and pylons, designed in Egypt to measure time, were probably built in the XIV century BC. A 35.5-metre high obelisk has survived to this day in St. Peter's Square in Rome, where it was delivered in 38 A.D. by Caligula from Heliopolis.
Changes in the length and direction of the shadow not only measured the time, but also observed the mutual movement of the Sun and the Earth. There is no doubt that mathematicians and astronomers of the pre-Pythagorean era, who also included Anaximander and Thales, used the results of measurements to study the movement of space bodies. Except for Babylonians, Egyptians and Greeks, other peoples, for example Hindus and Peruvian Incas were engaged in studying of movement of the Sun. Astronomical sundial of Incas had different forms. Some of them were similar to the slopingly installed stone discs, and others - the low multi-faceted stone column. Similar structures, the purpose of which is not fully clarified in all cases, were found in Europe. Near Wattmoor in Emsland, a group of stones was found arranged in a square, the largest of which was in the middle. Their location in the plan indicates that already in the prehistoric era they served to obtain data on the time with which the cult rites were associated. On the territory of Great Britain more than 200 similar objects remained till now. As a rule, it is a circular accumulation of stones with an altar located in the middle. For example, archaeological research in Staf-Fordshire revealed four large stones, located in the direction of the main countries of the world. The space bounded by these stones is crossed by an inclined stone, which was probably the main part of a large sundial. The position of these sundials allows, in addition to determining the time of day, the time of summer and winter solstice. However, the most interesting object of this kind is Stonehenge, located on the Salisburgh Plain in the central part of Great Britain, 132 km west of London. There are suggestions that the concentrically located group of stones and columns, surrounded by two rows of stones, was not only a place of worship for the Gauls, Britons and Irish, but also an astronomical device that determines the time of solstice. The appearance of this structure with an axis of symmetry formed by a wide path and a stone block called Friars Heels, above which the Sun always rises exactly on the day of the summer solstice, is attributed to the period of 1840...1680 BC *. The original appearance of the entire site in Stonehenge is a matter of course.