def flat2iso(s):
    """Converts a flat timestamp, like 20070221033032 to iso time-format.
    The format should be `YYYYMMDDhhmmss`
    """
    ts = '%s-%s-%sT%s:%s:%sZ' % (s[:4], s[4:6], s[6:8], s[8:10], s[10:12], s[12:14])
    return ts