def calc_dt_before_2005(y)
      t = y - 2000
      dt  = 63.86         + \
           ( 0.3345       + \
           (-0.060374     + \
           ( 0.0017275    + \
           ( 0.000651814  + \
           ( 0.00002373599) \
           * t) * t) * t) * t) * t
      return dt
    rescue => e
      raise
    end
def calc_dt_before_2005(y)
      t = y - 2000
      dt  = 63.86         + \
           ( 0.3345       + \
           (-0.060374     + \
           ( 0.0017275    + \
           ( 0.000651814  + \
           ( 0.00002373599) \
           * t) * t) * t) * t) * t
      return dt
    rescue => e
      raise
    end
=========================================================================
 deltaT (1986 <= year && year < 2005)

 @param:  y   (Year coefficient for deltaT calculation)
 @return: dt  (sec)
=========================================================================