def jd2tjm(jd):
    """
    Compute the time in Julian millennia since 2000.0.
    
    Args:
      jd (double):  Julian day (days).
    
    Returns:
      double:  tjm: Time in Julian millennia since 2000.0 (UT).
    
    """
    return (jd - 2451545.0) / 365250
