Convert Month (Synodic) (month (synodic)) to Year (Julian) (y (Julian)) 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 (Julian) (y (Julian))
A Julian year is defined as exactly 365.25 days, reflecting the structure of the Julian calendar introduced by Julius Caesar in 45 BCE. This calendar assumed a fixed year length with a leap year every four years. Although revolutionary in its simplicity, the Julian year overestimates the actual tropical year by about 11 minutes, causing the calendar date to drift slowly relative to the seasons—an issue that accumulated to more than 10 days by the 16th century. Astronomers still use the Julian year as a standardized unit for long-term timekeeping, especially when expressing stellar motions, orbital periods, and cosmological timescales. Its simplicity and fixed length make it ideal for scientific definition even though it is obsolete as a civil calendar.