def calc_dt_before_1860(y)
      t = y - 1800
      dt  = 13.72          + \
           (-0.332447      + \
           ( 0.0068612     + \
           ( 0.0041116     + \
           (-0.00037436    + \
           ( 0.0000121272  + \
           (-0.0000001699  + \
           ( 0.000000000875) \
           * t) * t) * t) * t) * t) * t) * t
      return dt
    rescue => e
      raise
    end
def calc_dt_before_1860(y)
      t = y - 1800
      dt  = 13.72          + \
           (-0.332447      + \
           ( 0.0068612     + \
           ( 0.0041116     + \
           (-0.00037436    + \
           ( 0.0000121272  + \
           (-0.0000001699  + \
           ( 0.000000000875) \
           * t) * t) * t) * t) * t) * t) * t
      return dt
    rescue => e
      raise
    end
=========================================================================
 deltaT (1800 <= year && year < 1860)

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