diff --git a/make_graphs.py b/make_graphs.py
index 2f56fb0..150d582 100644
--- a/make_graphs.py
+++ b/make_graphs.py
@@ -8,7 +8,6 @@ import csv
 import os
 import abc
 import datetime
-import multiprocessing
 import matplotlib.pyplot as pplot
 import sentry_sdk
 
@@ -166,7 +165,7 @@ class BirbAnalyzer(CsvAnalyzer):
                 item = {}
                 for (name, value) in items:
                     item[name] = value.strip()
-                sec = datetime.datetime.strptime(item['http_start_time'], '%Y-%m-%dT%H:%M:%S.%f').strftime("%H:%M:%S")
+                sec = datetime.datetime.strptime(item['mqtt_arrive_time'], '%Y-%m-%dT%H:%M:%S.%f').strftime("%H:%M:%S")
                 if sec not in responsepersec:
                     responsepersec[sec] = []
                 else: