diff --git a/ChangeLog b/ChangeLog
index 148081ed3d..e30796d314 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Aug 30 23:44:09 2009  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (find_time_t): use mktime for the first guess.
+
 Sun Aug 30 16:38:56 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (rb_enc_symname2_p): not depend on nul terminator.
diff --git a/time.c b/time.c
index 8a680c9f15..edff7ee7a3 100644
--- a/time.c
+++ b/time.c
@@ -1962,6 +1962,16 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
 
     find_dst = 0 < tptr->tm_isdst;
 
+#if defined(HAVE_MKTIME)
+    tm0 = *tptr;
+    if (!utc_p && (guess = mktime(&tm0)) != -1) {
+        tm = GUESS(&guess);
+        if (tm && tmcmp(tptr, tm) == 0) {
+            goto found;
+        }
+    }
+#endif
+
     tm0 = *tptr;
     if (tm0.tm_mon < 0) {
       tm0.tm_mon = 0;