 At times, this can cause the code to be relatively inefficient. </p>

        <p>For example, if one wanted to plot something every 3 hours in UTC time, it would be very simple: to get the
            next plot point, just add 10,800 to the epoch time: </p>
        <pre class="tty">next_ts = last_ts + 10800 </pre>
        <p>But, if one wanted to plot something for every 3 hours <em>in local time</em> (that is, at 0000, 0300, 0600,
            etc.), despite a possible DST change in the middle, then things