Patch #1417555: SimpleHTTPServer now returns Last-Modified headers.
diff --git a/Lib/BaseHTTPServer.py b/Lib/BaseHTTPServer.py
index 722b50c..1b3d4db 100644
--- a/Lib/BaseHTTPServer.py
+++ b/Lib/BaseHTTPServer.py
@@ -436,10 +436,11 @@
         """Return the server software version string."""
         return self.server_version + ' ' + self.sys_version
 
-    def date_time_string(self):
+    def date_time_string(self, timestamp=None):
         """Return the current date and time formatted for a message header."""
-        now = time.time()
-        year, month, day, hh, mm, ss, wd, y, z = time.gmtime(now)
+        if timestamp is None:
+            timestamp = time.time()
+        year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp)
         s = "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (
                 self.weekdayname[wd],
                 day, self.monthname[month], year,
diff --git a/Lib/SimpleHTTPServer.py b/Lib/SimpleHTTPServer.py
index ea10fb7..089936f 100644
--- a/Lib/SimpleHTTPServer.py
+++ b/Lib/SimpleHTTPServer.py
@@ -85,7 +85,9 @@
             return None
         self.send_response(200)
         self.send_header("Content-type", ctype)
-        self.send_header("Content-Length", str(os.fstat(f.fileno())[6]))
+        fs = os.fstat(f.fileno())
+        self.send_header("Content-Length", str(fs[6]))
+        self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
         self.end_headers()
         return f