The 2017 Total Solar Eclipse Will Be Historic — Here’s Why

The Eclipse Pattern – The Saros Cycle

Most, but not all, eclipses have an identical repeat eclipse roughly 18 years and 11 days after the first eclipse. This periodicity of solar eclipses is known as the Saros Cycle – it also applies to lunar eclipses. The precise calculations used to arrive at these figures are very complicated though their accuracy is easy to observe.