Treaties are cited according to chapter 8 of the AGLC4. Citing treaties describes the components of treaty citation.
Rule 8.3 Date Opened for Signature or Signed and Date of Entry into Force
Where a treaty is adopted by the United Nations General Assembly, the date of adoption is generally the date of conclusion.
The date a current treaty was opened for signature can be found on the United Nations Treaty Collection. Select Depositary and locate the treaty using a Title Search.
To check if a country has a reservation on a United Nations multilateral treaty check the United Nations Treaty Collection - Status of Treaties section.
Rule 8.4 Treaty Series lists the order of preference for citation of treaty series:
Chapter 9 is not used for treaties, but for documents of the United Nations, such as the Charter of the United Nations and official UN documents. Rule 9.6 provides a table of Commonly Cited Documents to serve as a citation guide.
[AGLC4 rule 9.2.4 example] Universal Declaration of Human Rights, GA Res 217A (III), UN GAOR, UN Doc A/810 (10 December 1948).