def calc_dt_before_2050(y)
      t = y - 2000
      dt  = 62.92    + \
           ( 0.32217 + \
           ( 0.005589) \
           * t) * t
      return dt
    rescue => e
      raise
    end
def calc_dt_before_2050(y)
      t = y - 2000
      dt  = 62.92    + \
           ( 0.32217 + \
           ( 0.005589) \
           * t) * t
      return dt
    rescue => e
      raise
    end
=========================================================================
 deltaT (2005 <= year && year < 2050)

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