code: def calc_periods(hour=0, minute=0):
      
      # Calculate the time intervals in a usable form
      period_end = datetime.datetime.utcnow().replace(hour=hour,
                                                      minute=minute,
                                                      second=0,
                                                      microsecond=0)
      period_start = period_end - datetime.timedelta(days=1)
  
      # period end should be slightly before the midnight.
      # hence, we subtract a second
      # this will force period_end to store something like:
      # datetime.datetime(2016, 5, 19, 23, 59, 59, 999999)
      # instead of:
      # datetime.datetime(2016, 5, 20,  0,  0,  0,      0)
      period_end -= datetime.timedelta(seconds=1)
  
      return (period_start, period_end)
docs: Returns a tuple of start_period and end_period.
  
      Assumes that the period is 24-hrs.
      Parameters:
          - `hour`: the hour from 0 to 23 when the period ends
          - `minute`: the minute from 0 to 59 when the period ends
      This method will calculate the end of the period as the closest hour/minute
      going backwards.
      It will also calculate the start of the period as the passed hour/minute
      but 24 hrs ago.
      Example, if we pass 0, 0 - we will get the events from 0:00 midnight of the
      day before yesterday until today's midnight.
      If we pass 2,0 - we will get the start time as 2am of the previous morning
      till 2am of today's morning.
      By default it's midnight.