diff --git a/src/timers.cc b/src/timers.cc
index 221b594a..2501bab9 100644
--- a/src/timers.cc
+++ b/src/timers.cc
@@ -212,8 +212,10 @@ std::string LocalDateTimeString() {
       offset_minutes *= -1;
       tz_offset_sign = '-';
     }
+
+    // Apply % 100 to hour to guarantee range [0, 99].
     tz_len = ::sprintf(tz_offset, "%c%02li:%02li", tz_offset_sign,
-        offset_minutes / 100, offset_minutes % 100);
+        (offset_minutes / 100) % 100, offset_minutes % 100);
     CHECK(tz_len == 6);
     ((void)tz_len); // Prevent unused variable warning in optimized build.
   } else {