Input (grade 13): From its invention in 1656 by Christiaan Huygens until the 1930s, the pendulum clock was the world's most precise timekeeper, accounting for its widespread use.
Output (grade 6): It was invented in 1656 by Christiaan Huygens. From the year 1656 until the 1930s, the pendulum clock was the world's most accurate way of keeping time.