dont working :/

Hi 

you can use a compute function for X_STUDIO_TOTAL_DAYS 

if record.x_studio_date_depart > record.x_studio_date_arrive:
    raise ValidationError('Depart should not be greater than the Arrive.')
else:
    start_date = datetime.strptime(record.x_studio_date_depart, '%Y-%m-%d')
    end_date = datetime.strptime(record.x_studio_date_arrive, '%Y-%m-%d')
    delta = end_date - start_date
    record.x_studio_total_days = delta.days

Regards