Parses given text and returns ``datetime.datetime`` instance or raises
    ``ValueError``.

    :param text: string of desired date/datetime or something more verbose,
      like *yesterday*, *2weeks 3days*, etc.

def parse_datetime(text):
    """
    Parses given text and returns ``datetime.datetime`` instance or raises
    ``ValueError``.

    :param text: string of desired date/datetime or something more verbose,
      like *yesterday*, *2weeks 3days*, etc.
    """

    text = text.strip().lower()

    INPUT_FORMATS = (
        '%Y-%m-%d %H:%M:%S',
        '%Y-%m-%d %H:%M',
        '%Y-%m-%d',
        '%m/%d/%Y %H:%M:%S',
        '%m/%d/%Y %H:%M',
        '%m/%d/%Y',
        '%m/%d/%y %H:%M:%S',
        '%m/%d/%y %H:%M',
        '%m/%d/%y',
    )
    for format in INPUT_FORMATS:
        try:
            return datetime.datetime(*time.strptime(text, format)[:6])
        except ValueError:
            pass

    # Try descriptive texts
    if text == 'tomorrow':
        future = datetime.datetime.now() + datetime.timedelta(days=1)
        args = future.timetuple()[:3] + (23, 59, 59)
        return datetime.datetime(*args)
    elif text == 'today':
        return datetime.datetime(*datetime.datetime.today().timetuple()[:3])
    elif text == 'now':
        return datetime.datetime.now()
    elif text == 'yesterday':
        past = datetime.datetime.now() - datetime.timedelta(days=1)
        return datetime.datetime(*past.timetuple()[:3])
    else:
        days = 0
        matched = re.match(
            r'^((?P<weeks>\d+) ?w(eeks?)?)? ?((?P<days>\d+) ?d(ays?)?)?$', text)
        if matched:
            groupdict = matched.groupdict()
            if groupdict['days']:
                days += int(matched.groupdict()['days'])
            if groupdict['weeks']:
                days += int(matched.groupdict()['weeks']) * 7
            past = datetime.datetime.now() - datetime.timedelta(days=days)
            return datetime.datetime(*past.timetuple()[:3])

    raise ValueError('Wrong date: "%s"' % text)