I try to call a JS function from my qweb im_chat.xml template via:

<t t-name="im_chat.Conversation_content">
   <t t-foreach="_.keys(list)" t-as="date">
    <div class="oe_im_chatview_date_separator">
    <!--<t t-esc="Date.parse(date).toString(Date.CultureInfo.formatPatterns.longDate)"/>-->
    <t t-esc="ToShamsi(parseInt('2015'), parseInt('8'), parseInt('22'), 'Long')"/>
    </div>
    <t t-foreach="list[date]" t-as="bubble">
    <t t-if="bubble[0].type === 'message'">
    <t t-call="im_chat.Conversation_message_bubble">
    <t t-set="messages" t-value="bubble"/>
    </t>
    </t>
    <t t-if="bubble[0].type === 'meta'">
    <t t-call="im_chat.Conversation_technical_bubble">
    <t t-set="messages" t-value="bubble"/>
    </t>
    </t>
    </t>
    </t>
</t>

my js file include:

function ToShamsi(grgYear,grgMonth,grgDay,Format)

{

  [...]

}

but odoo show me this error"

     Uncaught TypeError: undefined is not a function 

any suggestions?

Thank Before.