diff --git a/configure.ac b/configure.ac
index a6cf24072cf5..6d53e10626b7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15153,7 +15153,8 @@ EOF
         AC_MSG_RESULT([Ant lib directory found.])
     fi
 
-    ant_minver=1.6.0
+    # reproducible builds need the modificationtime parameter for the jar task introduced in 1.10.2
+    ant_minver=1.10.2
     ant_minminor1=`echo $ant_minver | cut -d"." -f2`
 
     AC_MSG_CHECKING([whether Ant is >= $ant_minver])
diff --git a/external/beanshell/ExternalProject_beanshell.mk b/external/beanshell/ExternalProject_beanshell.mk
index 604b3571fe44..cce25bd1d28b 100644
--- a/external/beanshell/ExternalProject_beanshell.mk
+++ b/external/beanshell/ExternalProject_beanshell.mk
@@ -13,13 +13,18 @@ $(eval $(call gb_ExternalProject_register_targets,beanshell,\
 	build \
 ))
 
+# older versions of ant expect SOURCE_DATE_EPOCH to be in milliseconds, so if set in environment
+# that also would take precedence over the -Dant.tstam.now property and fail. That can be a problem
+# if the variable is overridden/provided by exporting it in the env instead of passing it to make
+# as a parameter. To counteract that problem, explicitly unset it here.
 $(call gb_ExternalProject_get_state_target,beanshell,build) :
 	$(call gb_Trace_StartRange,beanshell,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-	unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+	unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 	$(ICECREAM_RUN) "$(ANT)" \
 		$(if $(verbose),-v,-q) \
 		-f build.xml \
+		$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 		-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 		-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 		-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/beanshell/UnpackedTarball_beanshell.mk b/external/beanshell/UnpackedTarball_beanshell.mk
index ba472ebda6f1..91ee76f499b2 100644
--- a/external/beanshell/UnpackedTarball_beanshell.mk
+++ b/external/beanshell/UnpackedTarball_beanshell.mk
@@ -22,6 +22,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,beanshell,\
 	external/beanshell/beanshell-invoke.patch \
 	external/beanshell/java9.patch.0 \
 	external/beanshell/applet.patch.0 \
+	external/beanshell/beanshell-jar-timestamps.patch.1 \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/beanshell/beanshell-jar-timestamps.patch.1 b/external/beanshell/beanshell-jar-timestamps.patch.1
new file mode 100644
index 000000000000..19671abe8b08
--- /dev/null
+++ b/external/beanshell/beanshell-jar-timestamps.patch.1
@@ -0,0 +1,23 @@
+diff -ur beanshell.org/build.xml beanshell/build.xml
+--- beanshell.org/build.xml	2026-06-24 14:37:04.303021292 +0000
++++ beanshell/build.xml	2026-06-24 14:42:15.878048543 +0000
+@@ -11,7 +11,9 @@
+ 		useful...
+ -->
+ <project name="beanshell" default="jarall" basedir=".">
+-
++   <tstamp>
++       <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
++   </tstamp>
+ <!-- Project Configuration -->
+ 
+ <property name="file" value=""/>
+@@ -433,7 +435,7 @@
+ 
+ 	<target name="jarall" depends="compile,_distdir">
+ 		<delete file="${all-jar}"/>
+-		<jar jarfile="${all-jar}">
++		<jar jarfile="${all-jar}" modificationtime="${jar.timestamp}">
+ 			<manifest>
+ 				<attribute name="Main-Class" value="bsh.Console" />
+ 				<attribute name="Specification-Title" value="${Specification-Title}" />
diff --git a/external/hsqldb/ExternalProject_hsqldb.mk b/external/hsqldb/ExternalProject_hsqldb.mk
index fb6dc4d49d71..ac24850e84b4 100644
--- a/external/hsqldb/ExternalProject_hsqldb.mk
+++ b/external/hsqldb/ExternalProject_hsqldb.mk
@@ -18,15 +18,20 @@ $(eval $(call gb_ExternalProject_register_targets,hsqldb,\
 # org.apache.tools.ant.types.Permissions.setSecurityManager) would otherwise throw an
 # UnsupportedOperationException (see <https://openjdk.java.net/jeps/411> "Deprecate the Security
 # Manager for Removal"):
+# older versions of ant expect SOURCE_DATE_EPOCH to be in milliseconds, so if set in environment
+# that also would take precedence over the -Dant.tstam.now property and fail. That can be a problem
+# if the variable is overridden/provided by exporting it in the env instead of passing it to make
+# as a parameter. To counteract that problem, explicitly unset it here.
 $(call gb_ExternalProject_get_state_target,hsqldb,build) :
 	$(call gb_Trace_StartRange,hsqldb,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(if $(JDK_SECURITYMANAGER_DISALLOWED_FOR_BUILD), \
 		    ANT_OPTS="$$ANT_OPTS -Djava.security.manager=allow") \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build/build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/hsqldb/UnpackedTarball_hsqldb.mk b/external/hsqldb/UnpackedTarball_hsqldb.mk
index 29bd33cb7860..c532b9cc2266 100644
--- a/external/hsqldb/UnpackedTarball_hsqldb.mk
+++ b/external/hsqldb/UnpackedTarball_hsqldb.mk
@@ -32,6 +32,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,hsqldb,\
 	external/hsqldb/patches/disable-dump-script.patch \
 	external/hsqldb/patches/abstract.patch \
 	external/hsqldb/patches/applet.patch.0 \
+	external/hsqldb/patches/hsqldb-jar-timestamps.patch.1 \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/hsqldb/patches/hsqldb-jar-timestamps.patch.1 b/external/hsqldb/patches/hsqldb-jar-timestamps.patch.1
new file mode 100644
index 000000000000..209897c46599
--- /dev/null
+++ b/external/hsqldb/patches/hsqldb-jar-timestamps.patch.1
@@ -0,0 +1,19 @@
+diff -ur hsqldb.org/build/build.xml hsqldb/build/build.xml
+--- hsqldb.org/build/build.xml	2026-06-24 11:33:53.281747718 +0000
++++ hsqldb/build/build.xml	2026-06-24 14:14:08.447370174 +0000
+@@ -19,6 +19,7 @@
+    <tstamp>
+        <format property="_tmpstamp" pattern="yyyy/MM/dd-hh:mm:ss"
+                locale="en"/>
++       <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
+    </tstamp>
+ 
+    <property name="build.label" value="private-${_tmpstamp}"/>
+@@ -626,6 +627,7 @@
+         <jar jarfile="lib/hsqldb.jar"
+              basedir="classes"
+              compress="true"
++             modificationtime="${jar.timestamp}"
+          >
+          <manifest>
+              <attribute name='Specification-Title' value='${hsqldb.title}'/>
diff --git a/external/java_websocket/ExternalProject_java_websocket.mk b/external/java_websocket/ExternalProject_java_websocket.mk
index 9d4a62d81183..513840683d00 100644
--- a/external/java_websocket/ExternalProject_java_websocket.mk
+++ b/external/java_websocket/ExternalProject_java_websocket.mk
@@ -16,10 +16,11 @@ $(eval $(call gb_ExternalProject_register_targets,java_websocket,\
 $(call gb_ExternalProject_get_state_target,java_websocket,build) :
 	$(call gb_Trace_StartRange,java_websocket,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/java_websocket/UnpackedTarball_java_websocket.mk b/external/java_websocket/UnpackedTarball_java_websocket.mk
index 1d05361a25f9..7f865eec72cf 100644
--- a/external/java_websocket/UnpackedTarball_java_websocket.mk
+++ b/external/java_websocket/UnpackedTarball_java_websocket.mk
@@ -24,6 +24,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,java_websocket,\
 	external/java_websocket/patches/0001-cid-1546341-Resource-leak-on-an-exceptional-path.patch \
 	external/java_websocket/patches/0001-cid-1545249-Bad-bit-shift-operation.patch \
 	external/java_websocket/patches/0001-cid-1546344-Dm-Dubious-method-used.patch \
+	external/java_websocket/patches/java-websocket-jar-timestamps.patch.1 \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/java_websocket/patches/java-websocket-jar-timestamps.patch.1 b/external/java_websocket/patches/java-websocket-jar-timestamps.patch.1
new file mode 100644
index 000000000000..3f7d0097c3a2
--- /dev/null
+++ b/external/java_websocket/patches/java-websocket-jar-timestamps.patch.1
@@ -0,0 +1,20 @@
+diff -ur java_websocket.org/build.xml java_websocket/build.xml
+--- java_websocket.org/build.xml	2026-06-24 15:32:09.431913892 +0000
++++ java_websocket/build.xml	2026-06-24 15:33:15.528712683 +0000
+@@ -1,4 +1,7 @@
+ <project default="all">
++    <tstamp>
++        <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
++    </tstamp>
+     <target name="all" depends="jar" />
+ 
+     <target name="compile">
+@@ -11,7 +14,7 @@
+ 
+     <target name="jar" depends="compile">
+         <mkdir dir="dist"/>
+-        <jar destfile="dist/java_websocket.jar">
++        <jar destfile="dist/java_websocket.jar" modificationtime="${jar.timestamp}">
+             <fileset dir="build/classes" includes="**/*.class" />
+         </jar>
+     </target>
diff --git a/external/jfreereport/ExternalProject_jfreereport_flow_engine.mk b/external/jfreereport/ExternalProject_jfreereport_flow_engine.mk
index fa90262e0d05..abd33f931f7d 100644
--- a/external/jfreereport/ExternalProject_jfreereport_flow_engine.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_flow_engine.mk
@@ -20,10 +20,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_flow_engine,\
 $(call gb_ExternalProject_get_state_target,jfreereport_flow_engine,build) :
 	$(call gb_Trace_StartRange,jfreereport_flow_engine,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dlibbase.jar=$(gb_UnpackedTarball_workdir)/jfreereport_libbase/dist/libbase-$(LIBBASE_VERSION).jar \
 			-Dlibformula.jar=$(gb_UnpackedTarball_workdir)/jfreereport_libformula/dist/libformula-$(LIBFORMULA_VERSION).jar \
diff --git a/external/jfreereport/ExternalProject_jfreereport_flute.mk b/external/jfreereport/ExternalProject_jfreereport_flute.mk
index 1a57167246c0..f4194345f8cc 100644
--- a/external/jfreereport/ExternalProject_jfreereport_flute.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_flute.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_flute,\
 $(call gb_ExternalProject_get_state_target,jfreereport_flute,build) :
 	$(call gb_Trace_StartRange,jfreereport_flute,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libbase.mk b/external/jfreereport/ExternalProject_jfreereport_libbase.mk
index 864b13ed1519..2ed6c80c2c55 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libbase.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libbase.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libbase,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libbase,build) :
 	$(call gb_Trace_StartRange,jfreereport_libbase,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libfonts.mk b/external/jfreereport/ExternalProject_jfreereport_libfonts.mk
index 6b7da7b5c52b..ff3bd2edb72a 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libfonts.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libfonts.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libfonts,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libfonts,build) :
 	$(call gb_Trace_StartRange,jfreereport_libfonts,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libformula.mk b/external/jfreereport/ExternalProject_jfreereport_libformula.mk
index 5211d54fbca9..7bf2e930ff3d 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libformula.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libformula.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libformula,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libformula,build) :
 	$(call gb_Trace_StartRange,jfreereport_libformula,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_liblayout.mk b/external/jfreereport/ExternalProject_jfreereport_liblayout.mk
index 8fc997806c4f..6ddb16b9c2f2 100644
--- a/external/jfreereport/ExternalProject_jfreereport_liblayout.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_liblayout.mk
@@ -28,10 +28,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_liblayout,\
 $(call gb_ExternalProject_get_state_target,jfreereport_liblayout,build) :
 	$(call gb_Trace_StartRange,jfreereport_liblayout,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dflute.jar=$(gb_UnpackedTarball_workdir)/jfreereport_flute/dist/flute-$(FLUTE_VERSION).jar \
 			-Dlibbase.jar=$(gb_UnpackedTarball_workdir)/jfreereport_libbase/dist/libbase-$(LIBBASE_VERSION).jar \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libloader.mk b/external/jfreereport/ExternalProject_jfreereport_libloader.mk
index 5c5964b9e17a..0f9d874cd9e3 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libloader.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libloader.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libloader,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libloader,build) :
 	$(call gb_Trace_StartRange,jfreereport_libloader,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_librepository.mk b/external/jfreereport/ExternalProject_jfreereport_librepository.mk
index 49d7e9497fb9..e66e548a28a8 100644
--- a/external/jfreereport/ExternalProject_jfreereport_librepository.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_librepository.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_librepository,\
 $(call gb_ExternalProject_get_state_target,jfreereport_librepository,build) :
 	$(call gb_Trace_StartRange,jfreereport_librepository,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libserializer.mk b/external/jfreereport/ExternalProject_jfreereport_libserializer.mk
index d0d37a59bded..e3e79cb2083c 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libserializer.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libserializer.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libserializer,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libserializer,build) :
 	$(call gb_Trace_StartRange,jfreereport_libserializer,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)." \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_libxml.mk b/external/jfreereport/ExternalProject_jfreereport_libxml.mk
index f79bf3731eac..015dfb684e98 100644
--- a/external/jfreereport/ExternalProject_jfreereport_libxml.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_libxml.mk
@@ -19,10 +19,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_libxml,\
 $(call gb_ExternalProject_get_state_target,jfreereport_libxml,build) :
 	$(call gb_Trace_StartRange,jfreereport_libxml,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/ExternalProject_jfreereport_sac.mk b/external/jfreereport/ExternalProject_jfreereport_sac.mk
index 807f30e37ab5..01454bd9a396 100644
--- a/external/jfreereport/ExternalProject_jfreereport_sac.mk
+++ b/external/jfreereport/ExternalProject_jfreereport_sac.mk
@@ -16,10 +16,11 @@ $(eval $(call gb_ExternalProject_register_targets,jfreereport_sac,\
 $(call gb_ExternalProject_get_state_target,jfreereport_sac,build) :
 	$(call gb_Trace_StartRange,jfreereport_sac,EXTERNAL)
 	$(call gb_ExternalProject_run,build,\
-		unset MSYS_NO_PATHCONV && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
+		unset MSYS_NO_PATHCONV SOURCE_DATE_EPOCH && JAVA_HOME=$(JAVA_HOME_FOR_BUILD) \
 		$(ICECREAM_RUN) "$(ANT)" \
 			$(if $(verbose),-v,-q) \
 			-f build.xml \
+			$(if $(SOURCE_DATE_EPOCH),-Dant.tstamp.now=$(SOURCE_DATE_EPOCH)) \
 			-Dbuild.label="build-$(LIBO_VERSION_MAJOR).$(LIBO_VERSION_MINOR).$(LIBO_VERSION_MICRO).$(LIBO_VERSION_PATCH)" \
 			-Dant.build.javac.source=$(JAVA_SOURCE_VER) \
 			-Dant.build.javac.target=$(JAVA_TARGET_VER) \
diff --git a/external/jfreereport/UnpackedTarball_jfreereport_flow_engine.mk b/external/jfreereport/UnpackedTarball_jfreereport_flow_engine.mk
index 92b827255ca0..f15d35db9407 100644
--- a/external/jfreereport/UnpackedTarball_jfreereport_flow_engine.mk
+++ b/external/jfreereport/UnpackedTarball_jfreereport_flow_engine.mk
@@ -21,6 +21,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,jfreereport_flow_engine,\
 	external/jfreereport/patches/flow-engine.patch \
 	external/jfreereport/patches/flow-engine_date_is_datetime.patch.1 \
 	external/jfreereport/patches/pentaho-reporting-flow-engine-0.9.4-remove-commons-logging.patch.1 \
+	external/jfreereport/patches/flow-engine-jar-timestamps.patch.1 \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/jfreereport/UnpackedTarball_jfreereport_liblayout.mk b/external/jfreereport/UnpackedTarball_jfreereport_liblayout.mk
index 9e01fcd7699b..db40a9f63750 100644
--- a/external/jfreereport/UnpackedTarball_jfreereport_liblayout.mk
+++ b/external/jfreereport/UnpackedTarball_jfreereport_liblayout.mk
@@ -20,6 +20,7 @@ $(eval $(call gb_UnpackedTarball_fix_end_of_line,jfreereport_liblayout,\
 $(eval $(call gb_UnpackedTarball_add_patches,jfreereport_liblayout,\
 	external/jfreereport/patches/liblayout.patch \
 	external/jfreereport/patches/liblayout-0.2.10-remove-commons-logging.patch.1 \
+	external/jfreereport/patches/liblayout-jar-timestamps.patch.1 \
 ))
 
 # vim: set noet sw=4 ts=4:
diff --git a/external/jfreereport/java/sac/build.xml b/external/jfreereport/java/sac/build.xml
index 0e85dff04f3a..7eea51ac9fa1 100644
--- a/external/jfreereport/java/sac/build.xml
+++ b/external/jfreereport/java/sac/build.xml
@@ -1,5 +1,7 @@
 <project name="sac" default="all" basedir=".">
-
+  <tstamp>
+    <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
+  </tstamp>
   <!-- Properties -->
 
   <property name="name" value="sac"/>
@@ -42,7 +44,7 @@
 
   <!-- Build jar archives -->
   <target name="jar" depends="classes">
-    <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}"/>
+    <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}" modificationtime="${jar.timestamp}"/>
   </target>
 
   <!-- Build the full JavaDocs -->
@@ -61,4 +63,4 @@
   <!-- Build everything -->
   <target name="all" depends="jar,javadoc"/>
 
-</project>
\ No newline at end of file
+</project>
diff --git a/external/jfreereport/patches/common_build.patch b/external/jfreereport/patches/common_build.patch
index b197f494e128..905b1cbda0f7 100644
--- a/external/jfreereport/patches/common_build.patch
+++ b/external/jfreereport/patches/common_build.patch
@@ -117,3 +117,25 @@
  
      <manifest file="${dist.manifest.file}" mode="update">
        <attribute name="Implementation-Title" value="${impl.title}" />
+diff -ur jfreereport_flute.org/common_build.xml jfreereport_flute/common_build.xml
+--- a/jfreereport_flute.org/common_build.xml	2026-06-24 14:47:35.842081102 +0000
++++ b/jfreereport_flute/common_build.xml	2026-06-24 15:07:49.965391582 +0000
+@@ -47,6 +47,9 @@
+ 
+ 
+ <project name="Pentaho Common Build" basedir="." default="dist" xmlns:ivy="antlib:org.apache.ivy.ant">
++   <tstamp>
++       <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
++   </tstamp>
+   <description>
+ -------------------------------------------------------------------------------
+      Common Build file provides tasks needed to perform a project build. 
+@@ -1160,7 +1163,7 @@
+ 	    Creates a jar file from the bin directory
+ 	    ====================================================================-->
+   <target name="jar" depends="compile,set-build.id,generate.manifest" description="Jars up the bin directory after a compile">
+-    <jar destfile="${dist.dir}/${ivy.artifact.id}-${project.revision}.jar" manifest="${dist.manifest.file}">
++    <jar destfile="${dist.dir}/${ivy.artifact.id}-${project.revision}.jar" manifest="${dist.manifest.file}" modificationtime="${jar.timestamp}">
+       <fileset dir="${classes.dir}" />
+     </jar>
+   </target>
diff --git a/external/jfreereport/patches/flow-engine-jar-timestamps.patch.1 b/external/jfreereport/patches/flow-engine-jar-timestamps.patch.1
new file mode 100644
index 000000000000..ccd867a751a6
--- /dev/null
+++ b/external/jfreereport/patches/flow-engine-jar-timestamps.patch.1
@@ -0,0 +1,20 @@
+diff -ur jfreereport_flow_engine.org/build.xml jfreereport_flow_engine/build.xml
+--- jfreereport_flow_engine.org/build.xml	2026-06-24 14:47:45.196052819 +0000
++++ jfreereport_flow_engine/build.xml	2026-06-24 14:50:20.231584057 +0000
+@@ -1,4 +1,7 @@
+ <project name="flow-engine" default="all" basedir=".">
++   <tstamp>
++       <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
++   </tstamp>
+ 
+    <!-- Properties -->
+    <property name="name" value="flow-engine"/>
+@@ -55,7 +58,7 @@
+    <target name="jar" depends="classes">
+      <copy file="devresource/META-INF/MANIFEST.MF" tofile="${build}/manifest.tmp" failonerror="false"/>
+      <manifest file="${build}/manifest.tmp" mode="update"/>
+-     <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}" manifest="${build}/manifest.tmp"/>
++     <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}" manifest="${build}/manifest.tmp" modificationtime="${jar.timestamp}"/>
+    </target>
+ 
+    <!-- Build the full JavaDocs -->
diff --git a/external/jfreereport/patches/liblayout-jar-timestamps.patch.1 b/external/jfreereport/patches/liblayout-jar-timestamps.patch.1
new file mode 100644
index 000000000000..161fe531ad56
--- /dev/null
+++ b/external/jfreereport/patches/liblayout-jar-timestamps.patch.1
@@ -0,0 +1,20 @@
+diff -ur jfreereport_liblayout.org/build.xml jfreereport_liblayout/build.xml
+--- jfreereport_liblayout.org/build.xml	2026-06-24 15:14:55.392091886 +0000
++++ jfreereport_liblayout/build.xml	2026-06-24 15:23:10.047571909 +0000
+@@ -1,4 +1,7 @@
+ <project name="liblayout" default="all" basedir=".">
++   <tstamp>
++       <format property="jar.timestamp" pattern="yyyy-MM-dd'T'HH:mm:ssXXX" timezone="UTC"/>
++   </tstamp>
+ 
+    <!-- Properties -->
+    <property name="name" value="liblayout"/>
+@@ -60,7 +63,7 @@
+    <target name="jar" depends="classes">
+      <copy file="devresource/META-INF/MANIFEST.MF" tofile="${build}/manifest.tmp" failonerror="false"/>
+      <manifest file="${build}/manifest.tmp" mode="update"/>
+-     <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}" manifest="${build}/manifest.tmp"/>
++     <jar jarfile="${build.lib}/${name}.jar" basedir="${build.classes}" manifest="${build}/manifest.tmp" modificationtime="${jar.timestamp}"/>
+    </target>
+ 
+    <!-- Build the full JavaDocs -->