diff --git a/datetimes.Rmd b/datetimes.Rmd
index 739a7e0..ae92270 100644
--- a/datetimes.Rmd
+++ b/datetimes.Rmd
@@ -388,7 +388,7 @@ Why is one day after 1pm on March 12, 2pm on March 13?! If you look carefully at
 
 ### Periods
 
-To solve this problem, lubridate provides __periods__. Periods are time spans but don't have a fixed length in seconds, instead they work with "human" times, like days and months. That allows them work in a more intuitive way:
+To solve this problem, lubridate provides __periods__. Periods are time spans but don't have a fixed length in seconds, instead they work with "human" times, like days and months. That allows them to work in a more intuitive way:
 
 ```{r}
 one_pm