diff --git a/lib/std/time/time.c3 b/lib/std/time/time.c3
index 66f3ede35..17456432c 100644
--- a/lib/std/time/time.c3
+++ b/lib/std/time/time.c3
@@ -13,7 +13,7 @@ const Duration MIN = 60 * SEC;
 const Duration HOUR = 60 * MIN;
 const Duration DAY = 24 * HOUR;
 const Duration WEEK = 7 * DAY;
-const Duration MONTH = 30 * WEEK;
+const Duration MONTH = 30 * DAY;
 const Duration YEAR = 36525 * DAY / 100;
 
 fn Duration us(long l) @inline => (Duration)l * US;