The below code is working in openerp 7

<record id="view_project_gantt" model="ir.ui.view">
    <field name="name">Project Gantt</field>
    <field name="model">project.test</field>
    <field name="type">calendar</field>
    <field name="arch" type="xml">
    <gantt date_stop="date_finished" date_start="date_start" string="Productions" default_group_by="routing_id" mode ="month">
        </gantt>
    </field>

</record>

    <record id="action_project_test" model="ir.actions.act_window">
            <field name="name">Project Test</field>
            <field name="res_model">project.test</field>
            <field name="view_type">form</field>
            <field name="view_mode">tree,form,gantt</field>     
    </record>

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