def is_year(s):
    """
    Checks to see if the string is likely to be a year or not.  In
    order to be considered to be a year, it must pass the following
    criteria:

    1. four digits
    2. first two digits are either 19 or 20.

    :param s: the string to check for "year-hood"

    :returns: ``True`` if it is a year and ``False`` otherwise.
    """
    if not s:
        return False

    if len(s) == 4 and s.isdigit() and \
            (s.startswith("19") or s.startswith("20")):
        return True
    return False