import re
.
.


def ISOdate(date):
    '''
        converts the following date string format to ISO (yyyy-mm-dd):
        28-okt-1924 (dutch month abbreviations)
        28 oct 1924 (english..)
         9/nov/2012 (single digit)
    '''

    shortmonths = [
        'jan', 'feb', 'mrt', 'apr', 'mei', 'jun',
        'jul', 'aug', 'sep', 'okt', 'nov', 'dec',
        'jan', 'feb', 'mar', 'apr', 'may', 'jun',
        'jul', 'aug', 'sep', 'oct', 'nov', 'dec'
        ]

    # Month abbrevs are only different march, may and october.

    pat = r'(d{1,2})s?[-/]?s?(w{3})s?[-/]?s?(d{4})'

    q = re.match(pat, date)
    if q:
        year = q.group(3)
        day = int(q.group(1))
        month = shortmonths.index(q.group(2).lower()) % 12 + 1
        return u'{}-{:02d}-{:02d}'.format(year, month, day)
    else:
        # just return input, date fields may be empty
        return date

year = int(q.group(3))
day = int(q.group(1))
month = shortmonths.index(q.group(2).lower()) % 12 + 1
d = datetime.datetime(year, month, day)
return u'{:%YY-%m-%d}'.format(d)