diff --git a/src/main/java/org/apache/commons/lang3/time/DateUtils.java b/src/main/java/org/apache/commons/lang3/time/DateUtils.java
index f45c4cefd..a1fd58c1e 100644
--- a/src/main/java/org/apache/commons/lang3/time/DateUtils.java
+++ b/src/main/java/org/apache/commons/lang3/time/DateUtils.java
@@ -54,6 +54,8 @@ public class DateUtils {
 
     /**
      * The UTC time zone (often referred to as GMT).
+     * Since a {@code TimeZone} is mutable and this is a "constant", it is
+     * essential that this object is not altered.
      */
     public static final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone("GMT");
     /**