diff --git a/src/racket/sconfig.h b/src/racket/sconfig.h
index fc2a524c35..e101001619 100644
--- a/src/racket/sconfig.h
+++ b/src/racket/sconfig.h
@@ -766,6 +766,11 @@
 #endif
 # define MZ_JIT_USE_MPROTECT
 
+#if defined(__x86_64__)
+/* work around a bug in localtime() in 10.6.8 */
+# define MIN_VALID_DATE_SECONDS -67768122973193999
+#endif
+
 # define FLAGS_ALREADY_SET
 
 #endif
@@ -1026,6 +1031,8 @@
 
  /* TIME_TYPE_IS_UNSIGNED converts time_t values as unsigned. */
 
+ /* MIN_VALID_DATE_SECONDS sets a minimum vald time in seconds. */
+
  /* PROCESS_FUNCTION adds (process ...) and (system ...) functions */
 
  /* DIR_FUNCTION adds (current-directory ...) function */
diff --git a/src/racket/src/fun.c b/src/racket/src/fun.c
index 4c15dd1ba1..12991cbe3d 100644
--- a/src/racket/src/fun.c
+++ b/src/racket/src/fun.c
@@ -8315,6 +8315,12 @@ static int month_offsets[12] = { 0, 31, 59, 90,
                                 243, 273, 304, 334 };
 #endif
 
+#ifdef MIN_VALID_DATE_SECONDS
+# define VALID_TIME_RANGE(x) ((x) >= MIN_VALID_DATE_SECONDS)
+#else
+# define VALID_TIME_RANGE(x) 1
+#endif
+
 static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
 {
   UNBUNDLE_TIME_TYPE lnow;
@@ -8366,7 +8372,8 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
   }
 
   if (scheme_get_time_val(secs, &lnow)
-      && ((UNBUNDLE_TIME_TYPE)(now = (CHECK_TIME_T)lnow)) == lnow) {
+      && (((UNBUNDLE_TIME_TYPE)(now = (CHECK_TIME_T)lnow)) == lnow)
+      && VALID_TIME_RANGE(lnow)) {
     int success;
 
 #ifdef USE_MACTIME