Odoo-Build/snippets/purchase.purchase_order_form.format_dates.xml

<data inherit_id="purchase.purchase_order_form" priority="50">
    <xpath expr="//field[@name='date_order']" position="attributes">
        <attribute name="options">{"show_time":false}</attribute>
        <attribute name="widget">datetime</attribute>
    </xpath>
    <xpath expr="//field[@name='date_approve']" position="attributes">
        <attribute name="options">{"show_time":false}</attribute>
        <attribute name="widget">datetime</attribute>
    </xpath>
    <xpath expr="//tree/field[@name='date_planned']" position="attributes">
        <attribute name="options">{"show_time":false}</attribute>
        <attribute name="widget">datetime</attribute>
    </xpath>
    <xpath expr="//div/field[@name='date_planned']" position="attributes">
        <attribute name="options">{"show_time":false}</attribute>
        <attribute name="widget">datetime</attribute>
    </xpath>
</data>