“Sothic Cycle” is the name given to the astrophysical discrepancy between the 365-day ancient Egyptian solar year and the heliacal rising of Sirius. An estimated duration of the cycle (1,461 years) has been used to more accurately date events in ancient Egyptian historical records, but fails to account for (1) the 400-year leap cycles which subtract extra leap days that accumulate as an artifact of leap years being useful only for a solar year of 365.25 days rather than the actual 365.2422 days, as well as (2) the precession of equinoxes, a cycle so-called because it desynchronizes any given constellation on the ecliptic from the spring equinox sunrise by one degree every 72 years (coming full circle in nearly 26,000 years). In this brief article I describe these complications and the mathematics that must be used to correct for the multi-decade error in the Sothic Cycle caused thereby.
