code: def _utc_float(self):
          
          tai = self.tai
          leap_dates = self.ts.leap_dates
          leap_offsets = self.ts.leap_offsets
          leap_reverse_dates = leap_dates + leap_offsets / DAY_S
          i = searchsorted(leap_reverse_dates, tai, 'right')
          return tai - leap_offsets[i] / DAY_S
docs: Return UTC as a floating point Julian date.