Find Out The Origins of the Leap Second

Due to a complex interplay of Earth’s and the moon’s gravitational fields, our planet’s rotation has gradually slowed over time.
It hasn’t been the designated length of one solar day—the time it takes Earth to make a full rotation, or slightly more than 86,400 seconds—since about 1820.
In the 20th century technological and astronomical advancements led more precise measurements of Earth orientation giving us more acute figures for a single rotation.
Utilizing a technique that relies on distant quasars to help determine Earth's celestial orientation, Coordinated Universal Time determined a minute discrepancy in our previously calculated rate of rotation.
Which led to the adoption of the leap second in 1972 that helps to correct this imprecision.