Limitation periods for claims involving dismissal usually begin when the dismissal “takes effect”. Generally a dismissal takes effect from the time the employee stops working, not the time that he or she is notified of the dismissal. So, if the employee works out the notice period, the dismissal will generally take effect at the end of the notice period, on the last day of work, even though the employee might have been notified of the dismissal at an earlier time.
The situation may be different where the employee is paid in lieu of notice. In that situation, the date that the dismissal takes effect may be the date that the employee was notified of the dismissal.