fn parse_extended_ymd(string: &str) -> Option<(i32, u32, u32)>Expand description
Parse the ISO 8601 signed extended-year form (±YYYY[Y...]-MM-DD) into
raw (year, month, day) components, without validating the calendar date.
The caller must have already verified that string begins with + or -;
the year must have at least 4 digits. Returns None if the shape is
malformed or any component fails to parse numerically.