fn parse_day(day: &[u8]) -> Option<u8> {
    match parse_2_digits(day) {
        Some(day) if day >= 1 && day <= 31 => Some(day),
        _ => None,
    }
}
/// Parse a 2-digit day
Parse a 2-digit day
Parse a 2 - digit day
fn parse_day(day: &[u8]) -> Option<u8> {
    match parse_2_digits(day) {
        Some(day) if day >= 1 && day <= 31 => Some(day),
        _ => None,
    }
}
fn parse_day ( day : & [ u8 ] ) -> Option < u8 > { match parse_2_digits ( day ) { Some ( day ) if day >= 1 && day <= 31 => Some ( day ) , _ => None , } }
Parse a 2-digit day
Parse a 2 - digit day
day
&[u8]