English 22 activity By LEiZE.A 3497 BCE Obelisk Period: 2500 BCE to 2500 Sundial Period: 2000 BCE to 2000 Water Clock 769 BCE Candle clock 1000 Mechanical Clock 1250 Sundglass 1490 Harrison timepiece 1520 Pendulum clock 1560 Digital clock 1955 Atomic clock