Custom Post Type Events Archive Grouped By Month

I’m currently trying to get my events listing code to print out headers by Month. So basically this:

October

• event
• event

September

• event
• event

etc…

Right now it just keeps echoing January. I think it might have something to do with the $currentMonth or the strtotime() but I’m not sure what. Any suggestions? I’ve been looking at this post to try and figure it out.

Thanks!

<?php 
    $args = array(
    'post_type' => 'events',
    'orderby' => 'meta_value',
    'meta_key' => 'tf_events_startdate',
    'order' => 'DESC'
    );

    $my_query = new WP_Query($args);

    if ($my_query->have_posts()) : while ($my_query->have_posts()) :
    $my_query->the_post();

    $custom = get_post_custom(get_the_ID());

    // dates
    $sd = $custom["tf_events_startdate"][0];
    $ed = $custom["tf_events_enddate"][0];

    // - local time format -
    $time_format = get_option('time_format');
    $stime = date($time_format, $sd);
    $etime = date($time_format, $ed);

    // set headers

    if(!isset($currentMonth) || $currentMonth != date("m", strtotime($sd))){
        $currentMonth = date("m", strtotime($sd));


     echo '<h2>'.date("F", strtotime($sd)).'</h2>';

    }?>


    <ul>
        <li>
        <strong><a href="<?php the_permalink();?>"><?php the_title();?></a></strong>
         <br />
        <?php // - determine if it's a new day -
        $longdate = date("l, M j, Y", $sd);
        if ($daycheck == null) { echo $longdate; }
        if ($daycheck != $longdate && $daycheck != null) { echo $longdate; } ?>
        <br />
        <?php echo $stime;?>
        <hr />


        </li>
    </ul>
    <?php endwhile; else: ?>
    <ul id="events">
    <li><?php _e('No Events Yet .'); ?></li>
    </ul>
    <?php endif; ?>