odoo/addons/hr_timesheet_sheet/hr_timesheet_sheet_demo.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data noupdate="1">
        
        <record id="sheet1" model="hr_timesheet_sheet.sheet">
            <field name="name">Sheet 1</field>
            <field name="user_id" ref="base.user_root"/>
            <field name="employee_id" ref="hr.employee1" />
            <field eval="time.strftime('%Y-%m-01', time.localtime(time.mktime(time.localtime()[0:2] + (0,)*7)-1))" name="date_from"/>
            <field eval="time.strftime('%Y-%m-15', time.localtime(time.mktime(time.localtime()[0:2] + (0,)*7)-1))" name="date_current"/>
            <field eval="time.strftime('%Y-%m-%d', time.localtime(time.mktime(time.localtime()[0:2] + (0,)*7)-1))" name="date_to"/>
        </record>

    </data>
</openerp>