International courts use the concept of ‘critical date' in the process of settling territorial disputes. Though the concept and theory of 'critical date' is introduced a long time ago and widely employed in international law, scholars dispute over whether it is only a judicial technique or an established principle of law. At any rate, since international courts, including International Court of Justice(ICJ) and its predecessor, namely, Permanent Court of International Justice(PCIJ), solve territorial disputes by setting up critical dates in many cases submitted to them, we have no choice but to examine the concept, function, some standards of critical date and the attitudes of international courts toward its doctrine. In relation to this work, it is also necessary to consider the possibility of establishing two or more critical dates or critical period in the same territorial dispute and its influence upon the issue of territorial sovereignty over Dokdo. Through these important undertakings, we could manage the Dokdo diplomacy in a more consistent, proactive and strategic way.