t_date_arr</span> <span class="o">=</span> <span class="p">[]</span>
    <span class="n">end_date_arr</span> <span class="o">=</span> <span class="p">[]</span>

    <span class="k">for</span> <span class="n">df_name</span> <span class="ow">in</span> <span class="n">universe_dict</span><span class="p">:</span>
        <span class="c1"># Finding the latest of the start dates for each series</span>
        <span class="n">start_date_arr</span><span class="o">.</span><span class="n">append</span><span class="p"