import re


def cleanDateString(dateString):
    """
    Removes characters in date string that will be disregarded when interpreting the date

    >>> cleanDateString("[18]42")
    '1842'

    >>> cleanDateString("vermutlich um 1900")
    'vermutlich um 1900'

    """
    s = re.sub('\[|\]', '', dateString)
    return s