Returns ``datetime.datetime`` from human readable strings

    >>> from datetime import date, timedelta
    >>> from dateutil.relativedelta import relativedelta
    >>> parse_human_datetime('2015-04-03')
    datetime.datetime(2015, 4, 3, 0, 0)
    >>> parse_human_datetime('2/3/1969')
    datetime.datetime(1969, 2, 3, 0, 0)
    >>> parse_human_datetime('now') <= datetime.now()
    True
    >>> parse_human_datetime('yesterday') <= datetime.now()
    True
    >>> date.today() - timedelta(1) == parse_human_datetime('yesterday').date()
    True
    >>> year_ago_1 = parse_human_datetime('one year ago').date()
    >>> year_ago_2 = (datetime.now() - relativedelta(years=1) ).date()
    >>> year_ago_1 == year_ago_2
    True

def parse_human_datetime(s):
    """
    Returns ``datetime.datetime`` from human readable strings

    >>> from datetime import date, timedelta
    >>> from dateutil.relativedelta import relativedelta
    >>> parse_human_datetime('2015-04-03')
    datetime.datetime(2015, 4, 3, 0, 0)
    >>> parse_human_datetime('2/3/1969')
    datetime.datetime(1969, 2, 3, 0, 0)
    >>> parse_human_datetime('now') <= datetime.now()
    True
    >>> parse_human_datetime('yesterday') <= datetime.now()
    True
    >>> date.today() - timedelta(1) == parse_human_datetime('yesterday').date()
    True
    >>> year_ago_1 = parse_human_datetime('one year ago').date()
    >>> year_ago_2 = (datetime.now() - relativedelta(years=1) ).date()
    >>> year_ago_1 == year_ago_2
    True
    """
    if not s:
        return None
    try:
        dttm = parse(s)
    except Exception:
        try:
            cal = parsedatetime.Calendar()
            parsed_dttm, parsed_flags = cal.parseDT(s)
            # when time is not extracted, we 'reset to midnight'
            if parsed_flags & 2 == 0:
                parsed_dttm = parsed_dttm.replace(hour=0, minute=0, second=0)
            dttm = dttm_from_timtuple(parsed_dttm.utctimetuple())
        except Exception as e:
            logging.exception(e)
            raise ValueError("Couldn't parse date string [{}]".format(s))
    return dttm