diff --git a/README.md b/README.md
index 5608899..46cfc25 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@
 	+ Call `*#06#` on your phone
 	+ Or find IMEI in system settings
 	+ Or use `adb shell dumpsys iphonesubinfo`
-+ Decrypt database and get decrypted_database.db
++ Decrypt database and get decrypted_database.db:
 ```
 ./decrypt_db.sh <path to EnMicroMsg.db> <imei> <uin>
 ```
diff --git a/plot_num_msg_by_time.py b/plot_num_msg_by_time.py
new file mode 100755
index 0000000..47bdf8b
--- /dev/null
+++ b/plot_num_msg_by_time.py
@@ -0,0 +1,37 @@
+#!/usr/bin/env python2
+# -*- coding: UTF-8 -*-
+# File: plot_num_msg_by_time.py
+# Date: Fri Nov 21 15:19:00 2014 +0800
+# Author: Yuxin Wu <ppwwyyxxc@gmail.com>
+
+from lib.Parser import WeChatDBParser
+from lib.utils import ensure_unicode
+
+from datetime import timedelta
+import numpy as np
+import matplotlib.pyplot as plt
+import sys, os
+
+if len(sys.argv) != 3:
+    sys.exit("Usage: {0} <path to decrypted_database.db> <name>".format(sys.argv[0]))
+
+every_k_days = 2
+db_file = sys.argv[1]
+name = ensure_unicode(sys.argv[2])
+
+parser = WeChatDBParser(db_file)
+parser.parse()
+msgs = parser.msgs_by_talker[name]
+times = [x.createTime for x in msgs]
+start_time = times[0]
+diffs = [(x - start_time).days for x in times]
+max_day = diffs[-1]
+
+width = 30
+numbers = range((max_day / width + 1) * width + 1)[::width]
+labels = [(start_time + timedelta(x)).strftime("%m/%d") for x in numbers]
+plt.xticks(numbers, labels)
+plt.xlabel("Date")
+plt.ylabel("Number of msgs in k days")
+plt.hist(diffs, bins=max_day / every_k_days)
+plt.show()