def set_year(datetime, new_year):
    """
    Change the year of a datetime to some new year. If datetime is a leapday then return None
    :param datetime.datetime datetime: Datetime object to change
    :param int new_year: The new year
    :return: A datetime with the same date as the original except the changed year
    """
    try:
        new_dt = datetime.replace(year=new_year)
    except ValueError:
        new_dt = None
    return new_dt
