use filled time calculate duration

freqtrade/optimize/backtesting.py

@@ -534,7 +534,7 @@ class Backtesting:
         if sell.sell_flag:
             trade.close_date = sell_candle_time
 
-            trade_dur = int((trade.close_date_utc - trade.open_date_utc).total_seconds() // 60)
+            trade_dur = int((trade.close_date_utc - trade.filled_date_utc).total_seconds() // 60)
             try:
                 closerate = self._get_close_rate(sell_row, trade, sell, trade_dur)
             except ValueError:

freqtrade/persistence/models.py

@@ -366,6 +366,10 @@ class LocalTrade():
         else:
             return self.amount
 
+    @property
+    def filled_date_utc(self):
+        return self.select_order('buy', is_open=False).order_filled_date.replace(tzinfo=timezone.utc)
+
     @property
     def open_date_utc(self):
         return self.open_date.replace(tzinfo=timezone.utc)