diff --git a/freqtrade/optimize/hyperopt_tools.py b/freqtrade/optimize/hyperopt_tools.py
index 90976d34e..439016c14 100755
--- a/freqtrade/optimize/hyperopt_tools.py
+++ b/freqtrade/optimize/hyperopt_tools.py
@@ -75,7 +75,7 @@ class HyperoptTools():
             if fn:
                 HyperoptTools.export_params(params, strategy_name, fn.with_suffix('.json'))
             else:
-                logger.warn("Strategy not found, not exporting parameter file.")
+                logger.warning("Strategy not found, not exporting parameter file.")
 
     @staticmethod
     def has_space(config: Dict[str, Any], space: str) -> bool:
diff --git a/freqtrade/optimize/optimize_reports.py b/freqtrade/optimize/optimize_reports.py
index 5dc8554c4..eefacbbab 100644
--- a/freqtrade/optimize/optimize_reports.py
+++ b/freqtrade/optimize/optimize_reports.py
@@ -325,8 +325,9 @@ def generate_strategy_stats(btdata: Dict[str, DataFrame],
                     key=lambda x: x['profit_sum']) if len(pair_results) > 1 else None
     worst_pair = min([pair for pair in pair_results if pair['key'] != 'TOTAL'],
                      key=lambda x: x['profit_sum']) if len(pair_results) > 1 else None
-    results['open_timestamp'] = results['open_date'].astype(int64) // 1e6
-    results['close_timestamp'] = results['close_date'].astype(int64) // 1e6
+    if not results.empty:
+        results['open_timestamp'] = results['open_date'].view(int64) // 1e6
+        results['close_timestamp'] = results['close_date'].view(int64) // 1e6
 
     backtest_days = (max_date - min_date).days
     strat_stats = {
diff --git a/freqtrade/plugins/pairlist/OffsetFilter.py b/freqtrade/plugins/pairlist/OffsetFilter.py
index 4579204d9..573a573a6 100644
--- a/freqtrade/plugins/pairlist/OffsetFilter.py
+++ b/freqtrade/plugins/pairlist/OffsetFilter.py
@@ -48,7 +48,7 @@ class OffsetFilter(IPairList):
         """
         if self._offset > len(pairlist):
             self.log_once(f"Offset of {self._offset} is larger than " +
-                          f"pair count of {len(pairlist)}", logger.warn)
+                          f"pair count of {len(pairlist)}", logger.warning)
         pairs = pairlist[self._offset:]
         self.log_once(f"Searching {len(pairs)} pairs: {pairs}", logger.info)
         return pairs
diff --git a/freqtrade/rpc/rpc.py b/freqtrade/rpc/rpc.py
index 538e95f40..e0aaefe50 100644
--- a/freqtrade/rpc/rpc.py
+++ b/freqtrade/rpc/rpc.py
@@ -761,7 +761,7 @@ class RPC:
         sell_signals = 0
         if has_content:
 
-            dataframe.loc[:, '__date_ts'] = dataframe.loc[:, 'date'].astype(int64) // 1000 // 1000
+            dataframe.loc[:, '__date_ts'] = dataframe.loc[:, 'date'].view(int64) // 1000 // 1000
             # Move open to seperate column when signal for easy plotting
             if 'buy' in dataframe.columns:
                 buy_mask = (dataframe['buy'] == 1)