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 27208260a35415e440b66c1ef4b3d8c116450ffb
Author: Bernhard M. Wiedemann <bwiedemann@suse.de>
Date:   Wed Dec 23 13:53:56 2020 +0100

    FOP-2854: Allow to override CreationDate and MetadataDate
    
    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 107dba9fa..6f93f3da1 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);
         }
 
diff --git a/fop-core/src/main/java/org/apache/fop/render/intermediate/IFRenderer.java b/fop-core/src/main/java/org/apache/fop/render/intermediate/IFRenderer.java
index 84e4e3a2c..022a7a7a6 100644
--- a/fop-core/src/main/java/org/apache/fop/render/intermediate/IFRenderer.java
+++ b/fop-core/src/main/java/org/apache/fop/render/intermediate/IFRenderer.java
@@ -544,7 +544,10 @@ public class IFRenderer extends AbstractPathOrientedRenderer {
         } else {
             xmpBasic.setCreatorTool(Version.getVersion());
         }
-        xmpBasic.setMetadataDate(new java.util.Date());
+        java.util.Date d = System.getenv("SOURCE_DATE_EPOCH") == null ?
+                new java.util.Date() :
+                new java.util.Date(1000 * Long.parseLong(System.getenv("SOURCE_DATE_EPOCH")));
+        xmpBasic.setMetadataDate(d);
         if (getUserAgent().getCreationDate() != null) {
             xmpBasic.setCreateDate(getUserAgent().getCreationDate());
         } else {
diff --git a/fop-core/src/main/java/org/apache/fop/render/pdf/PDFRenderingUtil.java b/fop-core/src/main/java/org/apache/fop/render/pdf/PDFRenderingUtil.java
index 1f383a29e..281eba87b 100644
--- a/fop-core/src/main/java/org/apache/fop/render/pdf/PDFRenderingUtil.java
+++ b/fop-core/src/main/java/org/apache/fop/render/pdf/PDFRenderingUtil.java
@@ -260,7 +260,10 @@ class PDFRenderingUtil {
         fopXMP.mergeInto(docXMP, exclude);
         XMPBasicAdapter xmpBasic = XMPBasicSchema.getAdapter(docXMP);
         //Metadata was changed so update metadata date
-        xmpBasic.setMetadataDate(new java.util.Date());
+        java.util.Date d = System.getenv("SOURCE_DATE_EPOCH") == null ?
+                new java.util.Date() :
+                new java.util.Date(1000 * Long.parseLong(System.getenv("SOURCE_DATE_EPOCH")));
+        xmpBasic.setMetadataDate(d);
         PDFMetadata.updateInfoFromMetadata(docXMP, pdfDoc.getInfo());
 
         PDFMetadata pdfMetadata = pdfDoc.getFactory().makeMetadata(