I need to generate an id with date
Format : AB{dd}{mm}{yy}00000 

I use an ir_sequence for the moment

Have you an idea to insert date in this num ?

in my class : 

 def _get_code(self, cr, uid,context, *args):
        obj_sequence = self.pool.get('ir.sequence')    
        return obj_sequence.next_by_code(cr, uid, 'project.issue.sequence', context=context)

 _columns = {
                'num':fields.char('Numéro',size=64,readonly=True),
...
    _defaults = {
                'num': _get_code,

...

in data.xml : 

<data noupdate="0">
        <record model="ir.sequence.type" id="project_issue_code_sequence">
            <field name="name">Code sequence Issue</field>
            <field name="code">project.issue.sequence</field>
        </record>
        <record model="ir.sequence" id="project_issue_sequence">
            <field name="name">Sequence For Issue</field>
            <field name="code">project.issue.sequence</field>
            <field name="active">TRUE</field>
            <field name="prefix">AB</field>
            <field name="number_increment">1</field>
            <field name="number_next">1000</field>
            <field name="implementation">standard</field>
        </record>