https://github.com/apache/xmlgraphics-fop/pull/65
partial fix for
https://issues.apache.org/jira/browse/FOP-2854
https://github.com/openSUSE/daps/issues/482

commit 0d3f0f9a473aad6f315fd60cc6ed1447afb791ef
Author: Bernhard M. Wiedemann <bwiedemann@suse.de>
Date:   Wed Dec 23 13:53:56 2020 +0100

    FOP-2854: Allow to override CreationDate
    
    Allow to override build date with SOURCE_DATE_EPOCH
    in order to make builds reproducible.
    See https://reproducible-builds.org/ for why this is good
    and https://reproducible-builds.org/specs/source-date-epoch/
    for the definition of this variable.
    
    This patch was done while working on reproducible builds for openSUSE.

diff --git a/fop-core/src/main/java/org/apache/fop/pdf/PDFMetadata.java b/fop-core/src/main/java/org/apache/fop/pdf/PDFMetadata.java
index 3af9af606..ff708e371 100644
--- a/fop-core/src/main/java/org/apache/fop/pdf/PDFMetadata.java
+++ b/fop-core/src/main/java/org/apache/fop/pdf/PDFMetadata.java
@@ -134,7 +134,9 @@ public class PDFMetadata extends PDFStream {
 
         //Set creation date if not available, yet
         if (info.getCreationDate() == null) {
-            Date d = new Date();
+            Date d = System.getenv("SOURCE_DATE_EPOCH") == null ?
+                new Date() :
+                new Date(1000 * Long.parseLong(System.getenv("SOURCE_DATE_EPOCH")));
             info.setCreationDate(d);
         }