There has been confusion on social media, with some Cook Islands and overseas government websites stating the holiday is on July 6.
The office of the Prime Minister clarified the public holiday date in newspaper advertisements.
According to the Public Holidays (Ra o te Ui Ariki) Amended Act 2013, the holiday is always observed on the first Friday of July.
The Cook Islands recognise the day to honour and acknowledge the traditional leaders, past and present.
The House of Ariki was first formed in 1967, but the fundamental traditions go back for centuries