diff --git a/docs/ics_format.txt b/docs/ics_format.txt
index 1b73b48..c29bc2c 100644
--- a/docs/ics_format.txt
+++ b/docs/ics_format.txt
@@ -14,3 +14,5 @@ DTEND;TZID=/freeassociation.sourceforge.net/Continent/City:
  20230909T093000
 
 This includes the continent and city of the used time zone.
+
+"DESCRIPTION:" is an optional field.