https://salsa.debian.org/java-team/maven-javadoc-plugin/blob/master/debian/patches/reproducible-footer.patch
for https://issues.apache.org/jira/browse/MJAVADOC-619

Description: Use the SOURCE_DATE_EPOCH variable to set the current year displayed in the javadoc footer
Author: Emmanuel Bourg <ebourg@apache.org>
Forwarded: no
--- a/src/main/java/org/apache/maven/plugins/javadoc/AbstractJavadocMojo.java
+++ b/src/main/java/org/apache/maven/plugins/javadoc/AbstractJavadocMojo.java
@@ -2821,6 +2821,20 @@
     private String getBottomText()
     {
         int currentYear = Calendar.getInstance().get( Calendar.YEAR );
+        if ( System.getenv("SOURCE_DATE_EPOCH") != null )
+        {
+            try
+            {
+                Calendar calendar = Calendar.getInstance( java.util.TimeZone.getTimeZone("UTC") );
+                calendar.setTimeInMillis(Long.parseLong( System.getenv("SOURCE_DATE_EPOCH") ) * 1000);
+                currentYear = calendar.get( Calendar.YEAR );
+            }
+            catch (Exception e)
+            {
+                e.printStackTrace();
+            }
+        }
+
         String year = String.valueOf( currentYear );
 
         String inceptionYear = project.getInceptionYear();