increase sampling date in order to avoid trade suspention

bot.py

@@ -206,7 +206,7 @@ async def now(message):
         except IndexError:
             time_begin = stock_mix.create_time.strftime("%Y%m%d")
         buf = io.BytesIO()
-        datetime_ref = (datetime.datetime.utcnow() - datetime.timedelta(days=9)).strftime("%Y%m%d") # refer to last trading day
+        datetime_ref = (datetime.datetime.utcnow() - datetime.timedelta(days=30)).strftime("%Y%m%d") # refer to last trading day
         stock_data, matrix_close_price = await mix_data_collector_async(stock_mix, time_begin=datetime_ref)
         profit_ratio, stock_profit_ratio = stock_mix.get_profit_ratio(stock_data, matrix_close_price, 
                                                                       date_ref='latest')