diff --git a/libc/tzcode/private.h b/libc/tzcode/private.h
index c30c711..494e142 100644
--- a/libc/tzcode/private.h
+++ b/libc/tzcode/private.h
@@ -328,15 +328,20 @@
 #define TYPE_SIGNED(type) (((type) -1) < 0)
 #endif /* !defined TYPE_SIGNED */
 
-/* The minimum and maximum finite time values.  */
-static time_t const time_t_min =
-  (TYPE_SIGNED(time_t)
-   ? (time_t) -1 << (CHAR_BIT * sizeof (time_t) - 1)
-   : 0);
-static time_t const time_t_max =
-  (TYPE_SIGNED(time_t)
-   ? - (~ 0 < 0) - ((time_t) -1 << (CHAR_BIT * sizeof (time_t) - 1))
-   : -1);
+#define TWOS_COMPLEMENT(t) ((t) ~ (t) 0 < 0)
+
+  /* Max and min values of the integer type T, of which only the bottom
+   *    B bits are used, and where the highest-order used bit is considered
+   *       to be a sign bit if T is signed.  */
+#define MAXVAL(t, b)            \
+      ((t) (((t) 1 << ((b) - 1 - TYPE_SIGNED(t)))     \
+          - 1 + ((t) 1 << ((b) - 1 - TYPE_SIGNED(t)))))
+#define MINVAL(t, b)            \
+      ((t) (TYPE_SIGNED(t) ? - TWOS_COMPLEMENT(t) - MAXVAL(t, b) : 0))
+
+/* The minimum and maximum finite time values.  This assumes no padding.  */
+static time_t const time_t_min = MINVAL(time_t, TYPE_BIT(time_t));
+static time_t const time_t_max = MAXVAL(time_t, TYPE_BIT(time_t));
 
 #ifndef INT_STRLEN_MAXIMUM
 /*