History

Sundials have been widely used in ancient times.  This type of clock can measure the time according to the angle or location of the shadow of a rod that is at a certain angle to the ground. 
 This type of clock, despite its age, has acceptable accuracy, and its precise types determine the apparent solar time with an error of up to 15 minutes (caused by the rotation of the Earth's rotation axis). 
 According to Herodotus, the prototypes of this type of watch go back to the Sumerian and Chaldean peoples and are at least 5000 years old.