Example: In [40]: array([1, 2], dtype('>l')).dtype Out[40]: dtype('>i8') In [41]: array([1, 2], dtype('<l')).dtype Out[41]: dtype('int64') In [42]: array([1, 2], dtype('>q')).dtype Out[42]: dtype('>i8') In [43]: array([1, 2], dtype('<q')).dtype Out[43]: dtype('int64') In [44]: array([1, 2], dtype('>M8[D]')).dtype Out[44]: dtype('>M8[D]') In [45]: array([1, 2], dtype('<M8[D]')).dtype Out[45]: dtype('<M8[D]') I rather like the '>i8' form with '<' if appropriate, although it's probably a bit late to do anything about it. The datetime requires a patch to generate the swapped form. Long term, it might be good to strive for consistency. Thoughts? Chuck.