def format_time(data, year):
    """Format any time variables in US.

    Parameters
    ----------
    data : pd.DataFrame
        Data without time formatting.
    year : int
        The `year` of the wave being processed.

    Returns
    -------
    data : pd.DataFrame
        Data with time formatting.
    """
    # See to do messages at the top of the file.
    # Theres some wierd overlap in the pidp data. Theres essentially a gap in September 2008 with noone in it from
    # BHPS which makes transition models fail.
    # Following 2 lines are a stupid work around.
    # if self.year <= 2008:
    #    self.year += 1
    data["time"] = year
    return data