diff --git a/collects/repo-time-stamp/.gitattributes b/collects/repo-time-stamp/.gitattributes
new file mode 100644
index 0000000000..9cdb23de2e
--- /dev/null
+++ b/collects/repo-time-stamp/.gitattributes
@@ -0,0 +1 @@
+/stamp.rkt ident export-subst
diff --git a/collects/repo-time-stamp/stamp.rkt b/collects/repo-time-stamp/stamp.rkt
index 7512066c3a..d39cb78600 100644
--- a/collects/repo-time-stamp/stamp.rkt
+++ b/collects/repo-time-stamp/stamp.rkt
@@ -1 +1,38 @@
-#lang scheme/base (provide stamp) (define stamp "17apr2010")
+#lang racket/base
+
+(provide stamp)
+
+(define archive-id "$Format:%ct|%h|a$")
+;; when exported through `git archive', the above becomes something like
+;; "1273562690|cabd414|a"
+
+(require racket/system racket/runtime-path)
+
+(define-runtime-path this "stamp.rkt")
+
+(define stamp
+  (let ([rx:secs+id #rx"^([0-9]+)\\|([0-9a-f]+)\\|(.*?)[ \r\n]*$"])
+    (for*/or ([x (list
+                  ;; info from an archive (incl. nightly builds)
+                  (lambda () archive-id)
+                  ;; try to run git to get the current info
+                  (lambda ()
+                    (let ([exe (or (find-executable-path "git")
+                                   (find-executable-path "git.exe"))])
+                      (and exe
+                           (let ([out (open-output-string)])
+                             (parameterize ([current-output-port out])
+                               (system* exe "log" "-1"
+                                        "--pretty=format:%ct|%h|g")
+                               (get-output-string out))))))
+                  ;; fallback: get the date of this file, no id
+                  (lambda ()
+                    (format "~a|0|f"
+                            (file-or-directory-modify-seconds this))))])
+      (let* ([x (x)]
+             [m (and (string? x) (regexp-match rx:secs+id x))]
+             [d (and m (seconds->date (string->number (cadr m))))])
+        (define (pad02 f) (let ([n (f d)]) (if (< n 10) (format "0~a" n) n)))
+        (and d (apply format "~a-~a-~a(~a/~a)"
+                      (date-year d) (pad02 date-month) (pad02 date-day)
+                      (cddr m)))))))