Convert Month (Synodic) (month (synodic)) to Year (Leap) (y (leap)) instantly.
About these units
Month (Synodic) (month (synodic))
A synodic month is the time the Moon takes to complete a full cycle of phases—from new moon to new moon—lasting about 29.53059 days. Unlike the simple geometric orbit of the Moon, the synodic period aligns with the Sun–Earth–Moon relationship, making it tied to how humans perceive the Moon's illumination cycle. This is the month that shaped nearly all ancient calendars, from Babylonian to Hebrew, Islamic, and Chinese systems. Religious festivals, agricultural cycles, and early navigation practices all relied on the regularity of the synodic month. Even today, while civil calendars use fixed months, astronomical calculations and lunar calendars still depend on synodic months to track tides, eclipse cycles, and the dynamics of Earth's only natural satellite. The synodic month illustrates how natural celestial rhythms guided early human civilization.
Year (Leap) (y (leap))
A leap year contains 366 days, occurring roughly every four years in the Gregorian calendar to correct for the fact that a tropical year is not exactly 365 days. Leap years prevent seasonal drift by compensating for the extra 0.2422 days in each solar year. Without leap-year corrections, seasons would shift by one full day every four years, eventually placing summer in December over the course of centuries. Leap years are essential to maintaining synchrony between human calendars and Earth's orbital mechanics, illustrating how civil timekeeping must regularly adjust for astronomical reality.