diff --git a/library/calendar.m b/library/calendar.m
index 6e8b19a6c..05128b5d0 100644
--- a/library/calendar.m
+++ b/library/calendar.m
@@ -22,7 +22,7 @@
 % a detailed description.) This is the calendar that is currently used
 % by most of the world.
 %
-% This modules allows times to be represented at microsecond resolution,
+% This module allows times to be represented at microsecond resolution,
 % though of course not all sources of time information are that precise.
 %
 %---------------------------------------------------------------------------%