<div class="wdn-grid-set">
    <section class="bp2-wdn-col-one-third">
        <?php echo $savvy->render($context, 'sidebar.tpl.php'); ?>
    </section>
    <section id="updatecontent" class="day_cal bp2-wdn-col-two-thirds">
        <?php
        echo $savvy->render($context, 'hcalendar/Day.tpl.php');
        ?>
    </section>
</div>

<div class="wdn-grid-set">
    <section class="bp1-wdn-col-one-third">
        <?php echo $savvy->render($context, 'sidebar.tpl.php'); ?>
    </section>
    <section id="updatecontent" class="day_cal bp1-wdn-col-two-thirds">
        <?php
        echo $savvy->render($context, 'hcalendar/Day.tpl.php');
        ?>
    </section>
</div>

--- 
+++ 
@@ -1,8 +1,8 @@
 <div class="wdn-grid-set">
-    <section class="bp1-wdn-col-one-third">
+    <section class="bp2-wdn-col-one-third">
         <?php echo $savvy->render($context, 'sidebar.tpl.php'); ?>
     </section>
-    <section id="updatecontent" class="day_cal bp1-wdn-col-two-thirds">
+    <section id="updatecontent" class="day_cal bp2-wdn-col-two-thirds">
         <?php
         echo $savvy->render($context, 'hcalendar/Day.tpl.php');
         ?>
Change grid breakpoints for the Day template