diff --git a/datetimes.qmd b/datetimes.qmd
index c687432..6a3ccf1 100644
--- a/datetimes.qmd
+++ b/datetimes.qmd
@@ -639,7 +639,7 @@ We can fix this by adding `days(1)` to the arrival time of each overnight flight
 flights_dt <- flights_dt |> 
   mutate(
     overnight = arr_time < dep_time,
-    arr_time = arr_time + days(!overnight),
+    arr_time = arr_time + days(overnight),
     sched_arr_time = sched_arr_time + days(overnight)
   )
 ```