diff --git a/README.md b/README.md
index 89b6818809099173cebc34829b36e31605fb54c8..e5f23beb81c9a81517c7d7fe1745a51d29137898 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,7 @@
 - Prepare: http://docs.fluentd.org/articles/before-install
 - Overview: http://docs.fluentd.org/articles/quickstart
 - Plugins: http://www.fluentd.org/plugins
+- Time Format: http://ruby-doc.org/core-1.9.3/Time.html#method-i-strftime
 
 # Preparing SSL Cert