| Year | date | Event |
|---|
| 1900 | 6 September | The request of the supreme arica of the Cook Islands for the inclusion of the archipelago into the British Empire . |
| 1900 | September 27 | The New Zealand Parliament approved the annexation of the Cook Islands. |
| 1901 | June 11 | Cook Islands became part of New Zealand. A general council has been formed - the first island government. |
| 1926 | | The first Seventh Day Adventists landed on Atiu Island. |
| 1964 | November 17 | The New Zealand Parliament passed the Constitutional Act of the Cook Islands . |
| 1965 | 20 April | Universal vote on the future status of the Cook Islands. |
| 1965 | August 4 | Adopted the Constitution of the Cook Islands. Obtaining the status of a self-governing territory in the Free Association of New Zealand. |
| 1965 | | The first Prime Minister of the Cook Islands, the leader of the Cook Islands Party , Albert Henry, was elected. |
| 1971 | | The Cook Islands have become a member of the Pacific Islands Forum . The Cook Islands first appeared as an independent subject of international law. |
| 1973 | 14th of April | The Cook Islands signed the Agreement on the South Pacific Economic Cooperation Bureau in Apia . |
| 1974 | | The first overseas representation of the Cook Islands has opened in Auckland, New Zealand . |
| 1976 | | Cook Islands have become a member of the Asian Development Bank . |
| 1977 | | The Ministry of Land and Foreign Affairs ( English Ministry of Planning and External Affairs ) first appeared on the Cook Islands. |
| 1979 | | Sir Albert Henry was accused of faking the results of the vote, for which he was deprived of the post of prime minister. The new prime minister becomes Tom Davis . |
| 1980 | June 11 | The Cook Islands and the United States signed the Treaty of Friendship and the Determination of Maritime Borders on the island of Rarotonga . |
| 1980 | 4th of July | The Cook Islands signed the South Pacific Regional Trade and Economic Cooperation Agreement . |
| 1980 | October 14 | The Cook Islands have become a full member of the South Pacific Commission . |
| 1981 | | An amendment to the Constitution of the Cook Islands, according to which the number of seats in parliament has increased from 22 to 24, and the parliamentary term from 4 to 5 years. |
| 1981 | January | Cook Islands declared neutral country. Refusal to join any military alliances. |
| 1984 | | In the Cook Islands, a Ministry of Foreign Affairs has been established . |
| 1984 | May 9 | The Cook Islands have become a full member of the World Health Organization . |
| 1985 | | In the capital of New Zealand, the city of Wellington , the first embassy of the Cook Islands was opened. |
| 1985 | March 19 | Honorary Consul of the Cook Islands was appointed to the city of Honolulu in the Hawaiian Islands . |
| 1985 | 11th of November | Appointed the first honorary consul in Europe - in the city of Oslo , the capital of Norway . |
| 1987 | February 10 | The Cook Islands have become a full member of the Food and Agriculture Organization of the United Nations . |
| 1989 | the 25th of October | The Cook Islands became a full member of UNESCO . |
| 1991 | | Signed an agreement on friendship and cooperation with France . |
| 1993 | January 22 | The Cook Islands have become a member of the International Fund for Agricultural Development . |
| 1995 | August 14 | The Cook Islands have become a member of the World Meteorological Organization . |
| 1997 | | Established diplomatic relations with the PRC . |
| 1997 | November | As a result of a tropical cyclone, 6 people died and 80% of the buildings were destroyed. |