Function worked_away 

pub fn worked_away(
    work: &[AdminWindow],
    held: &[(i64, i64)],
    date: Date,
    zone: &TimeZone,
    from: i64,
    to: i64,
) -> u32

Minutes of date‘s working time between from and to (Unix seconds): the working hours’ room as the plan counts it, less meals, naps and events.