diff --git a/suse-buildsystem.sh b/suse-buildsystem.sh
index 1f3dccf..7af4355 100644
--- a/suse-buildsystem.sh
+++ b/suse-buildsystem.sh
@@ -7,3 +7,51 @@ export QT_HASH_SEED=0
 export PERL_HASH_SEED=42
 export PYTHONHASHSEED=0
 export FORCE_SOURCE_DATE=1 # for texlive to use SOURCE_DATE_EPOCH
+
+if test ! -v SOURCE_DATE_EPOCH && test -f /.buildenv && test "Y" != "$(rpm --eval '%disable_obs_set_source_date_epoch')"; then
+    BROKEN_SOURCE_DATE_EPOCH="$(
+    . /.buildenv
+    if test -f "$TOPDIR/SOURCES/_scmsync.obsinfo" ; then
+        mtime="$(grep mtime "$TOPDIR/SOURCES/_scmsync.obsinfo" |cut -d ' ' -f 2)"
+        if test 1 -gt "$mtime" ; then
+            echo "WARNING mtime in \TOPDIR/SOURCES/_scmsync.obsinfo seems invalid as it is less than 1" >&2
+        fi
+    elif test -v BUILD_CHANGELOG_TIMESTAMP ; then
+        mtime=$BUILD_CHANGELOG_TIMESTAMP
+        if test 1 -gt "$mtime" ; then
+            echo "WARNING BUILD_CHANGELOG_TIMESTAMP in /.buildenv seems invalid as it is less than 1" >&2
+        fi
+    else
+        echo "WARNING could not set SOURCE_DATE_EPOCH, ensure mtime is in \$TOPDIR/SOURCES/_scmsync.obsinfo or BUILD_CHANGELOG_TIMESTAMP is set in /.buildenv" >&2
+    fi
+    echo "$mtime"
+    )"
+    if test -z "$BROKEN_SOURCE_DATE_EPOCH"; then
+        unset BROKEN_SOURCE_DATE_EPOCH
+    else
+        export BROKEN_SOURCE_DATE_EPOCH
+    fi
+    SOURCE_DATE_EPOCH="$(
+    . /.buildenv
+    if test -v BUILD_RELEASE && test -v BROKEN_SOURCE_DATE_EPOCH; then
+        counter="$(echo "$BUILD_RELEASE" |cut -d '.' -f 2)"
+        if test 1 -gt "$counter" ; then
+            echo "WARNING number after \".\" in BUILD_RELEASE in /.buildenv seems invalid as it is less than 1" >&2
+        fi
+        date=$(( BROKEN_SOURCE_DATE_EPOCH + counter ))
+        echo "setting SOURCE_DATE_EPOCH to $date" >&2
+    else
+        echo "WARNING could not set SOURCE_DATE_EPOCH, ensure BUILD_RELEASE is set in /.buildenv" >&2
+    fi
+    echo "$date"
+    )"
+    if test -z "$SOURCE_DATE_EPOCH"; then
+        unset SOURCE_DATE_EPOCH
+    else
+        export SOURCE_DATE_EPOCH
+    fi
+    if test "$SOURCE_DATE_EPOCH" -ge "$(date '+%s')" ; then
+        echo "ERROR SOURCE_DATE_EPOCH is in the future, clamping mtime if used might fail in hard to notice way, returning error" >&2
+        exit 1
+    fi
+fi