Constant calendrical_calculations::astronomy::MEAN_TROPICAL_YEAR

pub const MEAN_TROPICAL_YEAR: f64 = 365.242189;

The mean tropical year in days

This is defined in Calendrical Calculations by Reingold & Dershowitz. Reference lisp code: https://github.com/EdReingold/calendar-code2/blob/9afc1f3/calendar.l#L3872-L3874