Index: gap-4r8p3/cnf/mkversionheader.sh
===================================================================
--- gap-4r8p3.orig/cnf/mkversionheader.sh	2016-04-13 01:18:50.282856365 +0200
+++ gap-4r8p3/cnf/mkversionheader.sh	2016-04-13 12:48:29.000000000 +0200
@@ -10,7 +10,7 @@
     GAP_BUILD_VERSION=`git describe --tags --dirty || echo`
   fi
 fi
-GAP_BUILD_DATE=`date +"%Y-%m-%d %H:%M:%S (%Z)"`
+GAP_BUILD_DATE=`env LANG=C TZ=UTC date -d"@$SOURCE_DATE_EPOCH"  +"%Y-%m-%d %H:%M:%S (%Z)"`
 
 # Generate the file
 cat > "$TMP" <<EOF
