def jd2tjc(jd):
    """
    Compute the time in Julian centuries since 2000.0.
    
    Args:
      jd (double):  Julian day (days).
    
    Returns:
      double:  tjc: Time in Julian centuries since 2000.0 (UT).
    
    """
    return (jd - 2451545.0) / 36525
