diff --git a/functions/datetime.xml b/functions/datetime.xml
index f14639259d..63197738b0 100644
--- a/functions/datetime.xml
+++ b/functions/datetime.xml
@@ -218,7 +218,9 @@
       </listitem>
       <listitem>
        <simpara>
-        Z - timezone offset in seconds (i.e. "-43200" to "43200")
+		Z - timezone offset in seconds (i.e. "-43200" to "43200"). The offset
+		for timezones west of UTC is always negative, and for those east of
+		UTC is always positive.
        </simpara>
       </listitem>
      </itemizedlist>