REF: Revert daa1da9 and 52eb813 into something that works

Author: kernc

backtesting/_util.py

@@ -26,7 +26,11 @@ def _as_list(value):
 
 def _data_period(df):
     """Return data index period as pd.Timedelta"""
-    return df.index[:100].to_series(keep_tz=True).diff().median()
+    if df.index.is_all_dates:
+        values = df.index[:100].to_series(keep_tz=True)
+    else:
+        values = df.index[:100].to_series()
+    return values.diff().median()
 
 
 class _Array(np.ndarray):

backtesting/backtesting.py

@@ -870,8 +870,7 @@ def _drawdown_duration_peaks(dd, index):
         df['Drawdown Duration'] = dd_dur
         dd_dur = df['Drawdown Duration']
 
-        # Strip timezone info, otherwise pandas 0.24.2 errors when filling `s` ahead
-        df.index = data.index.tz_convert(None)
+        df.index = data.index
 
         def _round_timedelta(value, _period=_data_period(df)):
             if not isinstance(value, pd.Timedelta):