diff --git a/collects/tests/mzscheme/benchmarks/common/README.txt b/collects/tests/mzscheme/benchmarks/common/README.txt
index 96a9d4dec2..cc79243730 100644
--- a/collects/tests/mzscheme/benchmarks/common/README.txt
+++ b/collects/tests/mzscheme/benchmarks/common/README.txt
@@ -22,7 +22,9 @@ Naming no implementation/benchmark causes a standard of them to be run
 implementation/benchmak starts with "no-", the default set is used
 minus the "no-"-specified implementation/benchmark.
 
-The output is series of lines of the form
+The output is a comment line
+  ; <date and time>
+and then a series of lines of the form
   [<impl> <benchmark> (<cpu-msec> <real-msec> <gc-msec>) <compile-msec>]
 where #f means that the information is unavailable, or that the
 benchmark wasn't run due to an implementation limitation. The
diff --git a/collects/tests/mzscheme/benchmarks/common/auto.ss b/collects/tests/mzscheme/benchmarks/common/auto.ss
index f8f8de6ea7..40e2af1afa 100755
--- a/collects/tests/mzscheme/benchmarks/common/auto.ss
+++ b/collects/tests/mzscheme/benchmarks/common/auto.ss
@@ -9,6 +9,7 @@ exec mzscheme -qu "$0" ${1+"$@"}
            (lib "list.ss")
            (lib "compile.ss")
            (lib "inflate.ss")
+           (lib "date.ss")
            (lib "file.ss" "dynext"))
 
   ;; Implementaton-specific control functions ------------------------------
@@ -233,7 +234,7 @@ exec mzscheme -qu "$0" ${1+"$@"}
                            i))
                     impls)])
       (if (memq bm (impl-skips i))
-          (printf "[~a ~a ~s #f]\n" impl bm '(#f #f #f))
+          (rprintf "[~a ~a ~s #f]\n" impl bm '(#f #f #f))
           (let ([start (current-inexact-milliseconds)])
             ((impl-make i) bm)
             (let ([end (current-inexact-milliseconds)])
@@ -244,7 +245,7 @@ exec mzscheme -qu "$0" ${1+"$@"}
                                            [current-error-port out])
                               ((impl-run i) bm))
                       (error 'auto "~a\nrun failed ~a" (get-output-bytes out) bm))
-                    (printf "[~a ~a ~s ~a]\n"
+                    (rprintf "[~a ~a ~s ~a]\n"
                             impl
                             bm
                             ((impl-extract-result i) bm (get-output-bytes out))
@@ -253,6 +254,14 @@ exec mzscheme -qu "$0" ${1+"$@"}
             ((impl-clean-up i) bm)))
       (flush-output)))
 
+  (define (rprintf . args)
+    (apply printf args)
+    (when (current-output-file)
+      (with-output-to-file (current-output-file)
+        (lambda ()
+          (apply printf args))
+        'append)))
+
   (define no-implementations (map (lambda (s)
                                     (cons (string->symbol (format "no-~a" s))
                                           s))
@@ -269,6 +278,8 @@ exec mzscheme -qu "$0" ${1+"$@"}
   (define default-implementations (remq* obsolte-impls
                                          (map impl-name impls)))
 
+  (define current-output-file (make-parameter #f))
+
   ;; Extract command-line arguments --------------------
 
   (define args
@@ -288,6 +299,8 @@ exec mzscheme -qu "$0" ${1+"$@"}
        (for-each (lambda (bm)
                    (printf " ~a\n" bm))
                  benchmarks)]
+      [("-o" "--out") filename "append output to <filename>"
+       (current-output-file filename)]
       [("-n" "--iters") n "set number of run iterations"
        (let ([v (string->number n)])
          (unless (and (number? v)
@@ -340,6 +353,8 @@ exec mzscheme -qu "$0" ${1+"$@"}
 
   ;; Run benchmarks -------------------------------
 
+  (rprintf "; ~a\n" (date->string (seconds->date (current-seconds)) #t))
+
   (map (lambda (impl)
          (map (lambda (bm)
                 (run-benchmark impl bm))