diff --git a/freqtrade/optimize/backtesting.py b/freqtrade/optimize/backtesting.py
index 9b71dbfd9..cf140637c 100644
--- a/freqtrade/optimize/backtesting.py
+++ b/freqtrade/optimize/backtesting.py
@@ -4,11 +4,12 @@
 This module contains the backtesting logic
 """
 import logging
+import operator
 from argparse import Namespace
 from typing import Dict, Tuple, Any, List, Optional
 
 import arrow
-from pandas import DataFrame, Series
+from pandas import DataFrame
 from tabulate import tabulate
 
 import freqtrade.optimize as optimize
@@ -60,11 +61,12 @@ class Backtesting(object):
         :param data: dictionary with preprocessed backtesting data
         :return: tuple containing min_date, max_date
         """
-        all_dates = Series([])
-        for pair_data in data.values():
-            all_dates = all_dates.append(pair_data['date'])
-        all_dates.sort_values(inplace=True)
-        return arrow.get(all_dates.iloc[0]), arrow.get(all_dates.iloc[-1])
+        timeframe = [
+            (arrow.get(min(frame.date)), arrow.get(max(frame.date)))
+            for frame in data.values()
+        ]
+        return min(timeframe, key=operator.itemgetter(0))[0], \
+            max(timeframe, key=operator.itemgetter(1))[1]
 
     def _generate_text_table(self, data: Dict[str, Dict], results: DataFrame) -> str:
         """