calendar_holiday/views/hr_holidays_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="hr_holidays_form_view_inh_calendarholiday" model="ir.ui.view">
            <field name="name">hr.holidays.form.view.inh.calendarholiday</field>
            <field name="model">hr.holidays</field>
            <field name="inherit_id" ref="hr_holidays.edit_holiday_new"/>
            <field name="arch" type="xml">
                <field name="date_from" position="attributes">
                    <attribute name="on_change">onchange_date_from(date_to, date_from, employee_id)</attribute>
                </field>
                <field name="date_to" position="attributes">
                    <attribute name="on_change">onchange_date_to(date_to, date_from, employee_id)</attribute>
                </field>
                <field name="employee_id" position="attributes">
                    <attribute name="on_change">onchange_employee(employee_id, date_to, date_from)</attribute>
                </field>
            </field>
        </record>
    </data>
</openerp>