diff -urEbwB maven-source-plugin-3.3.1.orig/src/main/java/org/apache/maven/plugins/source/AbstractSourceJarMojo.java maven-source-plugin-3.3.1/src/main/java/org/apache/maven/plugins/source/AbstractSourceJarMojo.java
--- maven-source-plugin-3.3.1.orig/src/main/java/org/apache/maven/plugins/source/AbstractSourceJarMojo.java	2024-09-24 08:52:01.065274036 +0200
+++ maven-source-plugin-3.3.1/src/main/java/org/apache/maven/plugins/source/AbstractSourceJarMojo.java	2024-09-24 08:52:08.211989382 +0200
@@ -390,6 +390,14 @@
         archiver.setCreatedBy("Maven Source Plugin", "org.apache.maven.plugins", "maven-source-plugin");
         archiver.setBuildJdkSpecDefaultEntry(false);
 
+        if ( outputTimestamp == null ||
+            outputTimestamp.length() < 1 ||
+            ( ( outputTimestamp.length() == 1 )
+                && !Character.isDigit( outputTimestamp.charAt(0) ) ) )
+        {
+            outputTimestamp = System.getenv("SOURCE_DATE_EPOCH");
+        }
+
         // configure for Reproducible Builds based on outputTimestamp value
         archiver.configureReproducibleBuild(outputTimestamp);