Function nth_weekday_of_month 

pub fn nth_weekday_of_month(
    year: i64,
    month: u32,
    week: u32,
    weekday: u32,
) -> u32

The day-of-month of the week-th weekday of (year, month) — e.g. the 2nd Sunday of March, or (with week = 5) the last Sunday of October. week is 1..=5, weekday 0 = Sun … 6 = Sat.