diff --git a/datetimes.Rmd b/datetimes.Rmd
index 42c9600..55834ab 100644
--- a/datetimes.Rmd
+++ b/datetimes.Rmd
@@ -417,7 +417,7 @@ You can add and multiply periods:
 days(50) + hours(25) + minutes(2)
 ```
 
-And of course, add them to dates. Compared to durations, periods are more likely do what you expect:
+And of course, add them to dates. Compared to durations, periods are more likely to do what you expect:
 
 ```{r}
 # A leap year