anchor-based-lunisolar

Lunisolar calendar implementation using anchor dates derives year boundaries and leap rules from fixed Metonic cycles rather than astronomical events, applying real new-moon data for accurate month boundary calculations and visibility constraints.

Negative days and incorrect leap-month placement occur when year-resolution algorithms lack proper O(1) year calculations and fail to handle leap-year rules correctly before and after the established anchor date.

O(1) lunisolar date calculation requires deriving year boundaries and leap rules from a fixed anchor date and Metonic cycle, resolving years through explicit cycle math rather than iterating through astronomical events.

New-moon visibility rules determine lunisolar month boundaries by applying real new-moon data to establish when months begin, ensuring accurate date computation within Metonic cycle frameworks.

Anchor-based lunisolar calendars support historical systems like Babylonian, Hebrew, and Chinese by defining dates through explicit anchor dates and Metonic-type cycles with consistent leap-year handling.

Metonic cycle lunisolar calendars do not require astronomical event data for year boundaries; they use fixed cycle rules derived from an anchor date, though real new-moon data is needed for month boundaries.