Function calendrical_calculations::chinese_based::winter_solstice_on_or_before

pub(crate) fn winter_solstice_on_or_before<C: ChineseBased>(
    date: RataDie,
) -> RataDie

Get the fixed date of the nearest winter solstice, in the Chinese time zone, on or before a given fixed date.

This is valid for several thousand years, but it drifts for large positive and negative years. See bind_winter_solstice.

Based on functions from Calendrical Calculations by Reingold & Dershowitz. Lisp reference code: https://github.com/EdReingold/calendar-code2/blob/main/calendar.l#L5359-L5368