diff --git a/light_sensor_test.py b/light_sensor_test.py
index 5fc24c8..95ce6af 100755
--- a/light_sensor_test.py
+++ b/light_sensor_test.py
@@ -1,10 +1,19 @@
 #!/usr/bin/python2
 
 from light_sensor import light_sensor
-from time import sleep
+from time import sleep, time
+from datetime import datetime
 
 ls = light_sensor(1, 0x23)
 
 while True:
-	print "light: " + str(ls.read()) + " lx."
+	now = datetime.now()
+	now_str = str(now.year) + "-" + str(now.month) + "-" + str(now.day) + " " + str(now.hour) + ":" + str(now.minute) + ":" + str(now.second)
+	line = str(int(time())) + " " + now_str + " light: " + str(ls.read()) + " lx."
+	print line
+
+	log = open("light.log", "a")
+	log.write(line)
+	log.write("\n")
+	log.close()
 	sleep(1)