Function window_nests 

pub fn window_nests(fine: &str, coarse: &str) -> bool

Whether windows of width fine nest exactly in coarse: hours in a day, days in a week (Monday start) and in a month; weeks not in months. Windows are cut on the zoneless stored clock (UTC for zoned; see time_window_start), so no day has 23 or 25 hours and finer counts sum to the coarser.