Hello Aj,

For order_by, You can write when your model is define

Ex:-

class CustomClass(models.Model):

     _name = 'custom.class'

     _order = 'start_datetime desc'

For group_by, You can write search record for start_datetime

Ex:-

<record id="custom_class_search_view" model="ir.ui.view">

    <field name="name">custom.class.search.view</field>

    <field name="model">custom.class</field>

    <field name="arch" type="xml">

        <search string="Custom Class">       

            <filter name="group_start_datetime" string="Start time icon="terp-partner" context="{'group_by':'start_datetime'}"/>

        </search>

    </field>

</record>

Now You can pass in context of action as follow :-

<field name="context">{'search_default_group_start_datetime': 1}</field>

Hope it helps you.

Thanks,