Magento 1.9 Module – Form Submission Not Working

I have a custom admin module in my magento website. I use a custom form submission.
Here is my module.xml file

<?xml version="1.0"?>
<layout>
  <courses_adminhtml_book_update>
    <update handle="courses_book_update"/>
    <reference name="content">
       <block type="courses/adminhtml_update" name="update" template="courses/update.phtml"/>
    </reference>
  </courses_adminhtml_book_update>
</layout>

and here is my phtml file.

<div>
   <h3>Add Dates</h3><hr>
   <table cellspacing="0" class="form-list" id="date_tbl">
     <form id="edit_form" name="edit_form" method="post" action="<?=$this->getUrl('*/*/update')?>">
         <tr>
            <td class="label">New Date 1</td>
            <td class="input-ele"><input type="text" name="date[]" id="t1" /></td>
            <td class="img"><img src="<?=$this->getSkinUrl('images/grid-cal.gif')?>" alt="" class="v-middle" id="dt1" title="Date selector"></td>
        </tr>
        <tr id="date2">
            <td class="label">New Date 2</td>
            <td class="input-ele"><input type="text" name="date[]" id="t2" /></td>          <td class="img"><img src="<?=$this->getSkinUrl('images/grid-cal.gif')?>" alt="" class="v-middle" id="dt2" title="Date selector"></td>
        </tr>
        <tr id="date3">
            <td class="label">New Date 3</td>
            <td class="input-ele"><input type="text" name="date[]" id="t3" /></td>
            <td class="img"><img src="<?=$this->getSkinUrl('images/grid-cal.gif')?>" alt="" class="v-middle" id="dt3" title="Date selector"></td>
        </tr>
      </form>
    </table>
    <table cellspacing="0" class="form-list">
        <tr>
            <td class="label"><button onclick="editForm.submit()" class="scalable save" type="button"><span>Add Dates</span></button></td>
        </tr>
    </table>
</div>

<script type="text/javascript">
    var editForm = new varienForm('edit_form');
</script>

When I submit the form, it redirects to the admin home page (dashboard). What am I doing wrong? Please help me with this.