How will this scheduled event actually process? 

In the backtest log, I get the following result:

2017-02-21 09:31:00 :BTS

2017-02-21 09:31:00 :2017-02-21 09:00:00

self.Schedule.On(self.DateRules.EveryDay(), self.TimeRules.At(9, 0), Action(self.BeforeTradingStart))

def BeforeTradingStart(self):
# This is where we will run daily code checks to ensure lists are synced with positions.
# additionally, will determine how many days a position has been held in Portfolio
now = self.Time

So, whether backtesting, papertrading, or live trading, when is the function BeforeTradingStart actually executing? at 9:00 am, or 9:31 am?