Hi,

This message alert you that field day is not defined in model hr.attendance.

class hr_attendance(osv.osv):
    _name = "hr.attendance"    _description = "Attendance"
    _columns = {        
        'name': fields.datetime('Date', required=True, select=1),
        'action': fields.selection([('sign_in', 'Sign In'), ('sign_out', 'Sign Out'), ('action','Action')], 'Action', required=True),       
        'action_desc': fields.many2one("hr.action.reason", "Action Reason", domain="[('action_type', '=', action)]", help='Specifies the reason for Signing In/Signing Out in case of extra hours.'),        
        'employee_id': fields.many2one('hr.employee', "Employee", required=True, select=True),        
        'worked_hours': fields.function(_worked_hours_compute, type='float', string='Worked Hours', store=True),    }

So, try this instead:

att_obj = self.pool.get('hr.attendance')
att_id = att_obj.search(cr, uid, [('employee_id', '=', employee_id),('name', '=', time.strftime('%Y-%m-%d'))], limit=1, order='name desc')

Best regards