def truncate_window_length(universe_dict):
    """Chopping the length of all of the DataFrames to ensure
    that they are all between the same dates.

    :param universe_dict:           The dictionary of time series
    :type  universe_dict:           dict

    :return:                        the dictionary of truncated time series
    :rtype:                         dict
    """
    start_date_arr = []
    end_date_arr = []
    for df_name in universe_dict:
        start_date_arr.append(universe_dict[df_name].index[0])
        end_date_arr.append(universe_dict[df_name].index[-1])
    for df_name in universe_dict:
        df = universe_dict[df_name]
        universe_dict[df_name] = df.loc[(df.index <= min(end_date_arr)) & (
            df.index >= max(start_date_arr))]
    return universe_dict
