docs: def toJulian(dt=None):
      """Converts a Python datetime to a Julian date, using the formula from
      Meesus (1991).  This formula is reproduced in D.A. Vallado (2004).
  
      See:
  
          D.A. Vallado, Fundamentals of Astrodynamics and Applications, p. 187
          http://books.google.com/books?id=PJLlWzMBKjkC&lpg=PA956&vq=187&pg=PA187
      """
      if dt is None:
          dt = datetime.datetime.utcnow()
  
      if dt.month < 3:
          year  = dt.year  -  1
          month = dt.month + 12
      else:
          year  = dt.year
          month = dt.month
  
      A   = int(year / 100.0)
      B   = 2 - A + int(A / 4.0)
      C   = ( (dt.second / 60.0 + dt.minute) / 60.0 + dt.hour ) / 24.0
      jd  = int(365.25  * (year + 4716))
      jd += int(30.6001 * (month + 1)) + dt.day + B - 1524.5 + C
  
      return jd