Water clock
The use of water clocks in Persia or Greater Iran ,especially in desert area of Iran such as Yazd, Isfahan, and Gonabad,dates back to 500 BC. Later they were also used to say the exact time of holy days of pre-Islamic religions, such as telling  the time of the  equal day and night ( Nowruz), Chelah, or Yaldā – the shortest, longest, and equal-length days and nights of the years. The water clocks used in Iran were one of the most practical ancient tools for timing the yearly calendar.