clippy

src/date.rs

@@ -89,7 +89,7 @@ fn nth_weekday_of_month(year: i32, month: u32, week_day: Weekday, nth: i32) -> O
     }
     while date.month() == month {
         dates.push(date);
-        date = date + Duration::weeks(1);
+        date += Duration::weeks(1);
     }
     // get the right one
     let index = if nth < 0 { dates.len() as i32 + nth } else { nth - 1 } as usize;