Abstract： The critical date has been gradually introduced and applied in practice since the 1920s. The
critical date means that all the substantive facts relating to a dispute have occurred and that what
happens after the critical date cannot change the existing situation on the critical date. The rights of
the parties also depend on the situation on the critical date. The crux of the critical date is how to
make a proper determination. The core role of the critical date is that it has an important impact on the
admissibility and probative force of the evidence. The practice of the critical date in international
judicial and arbitral proceedings is of great significance for China to safeguard Chinas sovereignty
over her islands.