def timeuntil(d, now=None):
    """
    Like timesince, but returns a string measuring the time until
    the given time.
    """
    if not now:
        if getattr(d, 'tzinfo', None):
            now = datetime.datetime.now(LocalTimezone(d))
        else:
            now = datetime.datetime.now()
    return timesince(now, d)