diff --git a/datetimes.Rmd b/datetimes.Rmd
index 5bd1129..75dcd9c 100644
--- a/datetimes.Rmd
+++ b/datetimes.Rmd
@@ -486,7 +486,7 @@ 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 * 1),
+    arr_time = arr_time + days(ifelse(overnight, 0, 1)),
     sched_arr_time = sched_arr_time + days(overnight * 1)
   )
 ```