How does the saros cycle help predict eclipses?

The saros is an astronomical interval of approximately 18 years and 11 days that allows for the prediction of solar eclipses and lunar eclipses by identifying when the Sun, Moon, and Earth return to nearly identical relative positions.12

This cycle functions through a resonance between the synodic month (the interval between new moons) and the draconic month (the time taken for the Moon to return to the same orbital node). Because a saros consists of 223 synodic months—a duration that is also nearly equal to 242 draconic months—the Moon is positioned very close to a node at the start and end of the period, which is a requirement for an eclipse to occur.2

Additionally, the saros encompasses nearly a whole number of anomalistic months, meaning the Moon’s distance from Earth remains consistent, resulting in similar eclipse durations and appearances. While eclipses recur after each saros, the extra one-third of a day causes each subsequent event to shift approximately 120° westward on Earth's surface.23