Hello Chriskub,

Solution
=============

Try this below code, 

<template id="portal_order_page_x_informed_date" name="Orders X Informed Date" inherit_id="sale.portal_order_page">
        <xpath expr="//span[@t-field='order.create_date']/.." position="after">
            <div class="mb8">
                  <strong>X Informed Date:</strong> <span t-field="order.x_informed_date" t-options='{"widget": "date"}'/>
              </div>
        </xpath>
</template>

I hope my answer is helpful.

If any query so comment please.