'Callback triggered by the simulation loop whenever the current dt
changes.
Any logic that should happen exactly once at the start of each datetime
group should happen here.'

def on_dt_changed(self, dt):

    self.datetime = dt
    self.perf_tracker.set_date(dt)
    self.blotter.set_date(dt)
    self.portfolio_needs_update = True
    self.account_needs_update = True
    self.performance_needs_update = True
