def _is_julian( y, m, d ):      
    """
    The `_is_julian` function determines whether the input date is in the range 
    of the Julian date calender or not.
    
    Returns a boolean.
    """
    ret = False
    if y<1582:
        ret = True
    if y==1582 and m<10:
        ret = True
    if y==1582 and m==10 and d<=4:
        ret = True
    return ret