def ambiguous_date_to_date_range(mydate, fmt="%Y-%m-%d", min_max_year=None):
    """parse an abiguous date such as 2017-XX-XX to [2017,2017.999]

    Parameters
    ----------
    mydate : str
        date string to be parsed
    fmt : str
        format descriptor. default is %Y-%m-%d
    min_max_year : None, optional
        if date is completely unknown, use this as bounds.

    Returns
    -------
    tuple
        upper and lower bounds on the date. return (None, None) if errors
    """
    from datetime import datetime
    sep = fmt.split('%')[1][-1]
    min_date, max_date = {}, {}
    today = datetime.today().date()

    for val, field  in zip(mydate.split(sep), fmt.split(sep+'%')):
        f = 'year' if 'y' in field.lower() else ('day' if 'd' in field.lower() else 'month')
        if 'XX' in val:
            if f=='year':
                if min_max_year:
                    min_date[f]=min_max_year[0]
                    if len(min_max_year)>1:
                        max_date[f]=min_max_year[1]
                    elif len(min_max_year)==1:
                        max_date[f]=4000 #will be replaced by 'today' below.
                else:
                    return None, None
            elif f=='month':
                min_date[f]=1
                max_date[f]=12
            elif f=='day':
                min_date[f]=1
                max_date[f]=31
        else:
            try:
                min_date[f]=int(val)
                max_date[f]=int(val)
            except ValueError:
                print("Can't parse date string: "+mydate, file=sys.stderr)
                return None, None
    max_date['day'] = min(max_date['day'], 31 if max_date['month'] in [1,3,5,7,8,10,12]
                                           else 28 if max_date['month']==2 else 30)
    lower_bound = datetime(year=min_date['year'], month=min_date['month'], day=min_date['day']).date()
    upper_bound = datetime(year=max_date['year'], month=max_date['month'], day=max_date['day']).date()
    return (lower_bound, upper_bound if upper_bound<today else today)