diff --git a/source/time.tex b/source/time.tex
index 8000d75afa..c788fcf12b 100644
--- a/source/time.tex
+++ b/source/time.tex
@@ -10793,7 +10793,7 @@
 the locale's alternative full year representation.
 \\ \rowsep
 \tcode{\%z} &
-The offset from UTC in the ISO 8601:2004 format.
+The offset from UTC as specified in ISO 8601:2004, subclause 4.2.5.2.
 For example \tcode{-0430} refers to 4 hours 30 minutes behind UTC\@.
 If the offset is zero, \tcode{+0000} is used.
 The modified commands \tcode{\%Ez} and  \tcode{\%Oz}