fn parse_date_to_days(string: &str) -> Option<i32>Expand description
Parse a date string into days since 1970-01-01, covering the full
Date32 range (years ≈ ±5,881,580) for the signed extended-year form.
The Gregorian calendar repeats exactly every 400 years (146,097 days), so
we fold the year into [0, 400), validate the folded date, and add
era * 146_097 to recover the absolute day count.
For all other inputs, behavior matches parse_date.