Odoo-Build/snippets/project.view_task_form2.show_gantt_dates.xml

<data inherit_id="project.view_task_form2" priority="50">
    <field name="date_deadline" position="after">
        <label for="planned_date_begin" string="Planned Date"/>
        <div class="w-100">
            <div class="o_row">
                <field name="planned_date_begin" widget="daterange" options="{&quot;related_end_date&quot;: &quot;planned_date_end&quot;}"/>
                <i class="fa fa-long-arrow-right mx-2 oe_edit_only" aria-label="Arrow icon" title="Arrow"/>
                <i class="fa fa-long-arrow-right mx-2 oe_read_only" aria-label="Arrow icon" title="Arrow" attrs="{'invisible': [('planned_date_begin', '=', False), ('planned_date_end', '=', False)]}"/>
                <field name="planned_date_end" widget="daterange" options="{&quot;related_start_date&quot;: &quot;planned_date_begin&quot;}"/>
            </div>
        </div>
    </field>
</data>