Function parse_calendar_year_full_extended_range 

pub(crate) fn parse_calendar_year_full_extended_range(
    input: &[u8],
    modifiers: CalendarYearFullExtendedRange,
) -> Option<ParsedItem<'_, i32>>

Available on crate feature parsing only.

Parse the full calendar-based year.

This permits utilizing the full range of supported years, though at the cost of introducing parsing ambiguities.