diff --git a/check_log_ng.py b/check_log_ng.py
index 4475767..c7aa108 100755
--- a/check_log_ng.py
+++ b/check_log_ng.py
@@ -35,6 +35,7 @@
 import base64
 import fcntl
 import warnings
+from datetime import datetime
 
 FALLBACK_PATH = "/usr/local/hb-agent/bin"
 
@@ -745,9 +746,19 @@ def _get_cache(self, cachefile):
             line = fileobj.readline()
             fileobj.close()
         state, message = line.split("\t", 1)
+        cache_created_at = self._get_cache_created_at(cachefile)
+        message = "{0} (use cache created at {1})".format(message, cache_created_at)
         _debug("cache: state={0}, message='{1}'".format(state, message))
         return int(state), message
 
+    def _get_cache_created_at(self, cachefile):
+        """Get the cache's created time
+
+        Returns:
+            string representing the in ISO 8601 format (YYYY-MM-DDThh:mm:ss.ffffff).
+        """
+        return datetime.fromtimestamp(os.stat(cachefile).st_mtime).isoformat()
+
     def _update_cache(self, cachefile):
         """Update the cache."""
         if self.config['dry_run']:
diff --git a/test_check_log_ng.py b/test_check_log_ng.py
index 30f6347..bd5d2fe 100755
--- a/test_check_log_ng.py
+++ b/test_check_log_ng.py
@@ -24,6 +24,7 @@ class LogCheckerTestCase(unittest.TestCase):
     # Class constant
     MESSAGE_OK = "OK - No matches found."
     MESSAGE_WARNING_ONE = "WARNING: Found 1 lines (limit=1/0): {0} at {1}"
+    MESSAGE_WARNING_ONE_WITH_CACHE = "WARNING: Found 1 lines (limit=1/0): {0} at {1} (use cache created at {2})"
     MESSAGE_WARNING_ONE_WITH_QUIET = "WARNING: Found 1 lines (limit=1/0, QUIET): at {0}"
     MESSAGE_WARNING_ONE_WITH_HEADER = "WARNING: Found 1 lines (limit=1/0, HEADER): {0} at {1}"
     MESSAGE_WARNING_TWO = "WARNING: Found 2 lines (limit=1/0): {0},{1} at {2}"
@@ -1037,9 +1038,10 @@ def test_cachetime(self):
         log.check(self.logfile)
 
         self.assertEqual(log.get_state(), LogChecker.STATE_WARNING)
+        cache_created_at = log._get_cache_created_at(cachefile)
         self.assertEqual(
             log.get_message(),
-            self.MESSAGE_WARNING_ONE.format(line, self.logfile))
+            self.MESSAGE_WARNING_ONE_WITH_CACHE.format(line, self.logfile, cache_created_at))
 
         log._remove_cache(cachefile)
 
@@ -1112,9 +1114,10 @@ def test_cachetime_with_dry_run(self):
         log.check(self.logfile)
 
         self.assertEqual(log.get_state(), LogChecker.STATE_WARNING)
+        cache_created_at = log._get_cache_created_at(cachefile)
         self.assertEqual(
             log.get_message(),
-            self.MESSAGE_WARNING_ONE.format(line, self.logfile))
+            self.MESSAGE_WARNING_ONE_WITH_CACHE.format(line, self.logfile, cache_created_at))
 
         log._remove_cache(cachefile)