Function days_to_f64 

pub(crate) fn days_to_f64(days: i64) -> f64

Converts a whole-day count to f64.

Exact. chrono’s representable date range spans roughly ±262,000 years, so a day count is bounded by about 1e8 — six orders of magnitude inside f64’s exact-integer range of 2^53. No day count arising from two representable dates can lose precision here.