Besides the 11 confirmed atolls and islands, Filippo Reef is shown on some maps, but its existence is doubted.

The first whaler recorded to have visited one of them was the Coquette, which docked at Kiritimati (then called Christmas Island) in 1822.

It relinquished these claims only in 1979, when it entered into the Treaty of Tarawa, which recognised Kiribati's sovereignty over the majority of the Line Islands chain.

This adjustment effectively moved the International Date Line more than 1,000 km (620 mi) to the east within Kiribati, which placed all of Kiribati on the Asian or western side of the date line, despite the fact that Millennium Island's longitude of 150 degrees west corresponds to UTC−10:00 rather than to its official time zone of UTC+14:00.

[14] This move made Millennium Island (then Caroline Island) the easternmost land in the earliest time zone (by some definitions, the easternmost point on Earth), and one of the first points of land which saw sunrise on 1 January 2000 – at 5:43 am, as measured by local time.

[15] Other Pacific nations, including Tonga and New Zealand's Chatham Islands, protested the move, objecting that it interfered with their own claims to be the first land to see dawn in the year 2000.

[17] Over 70 Kiribati singers and dancers travelled to Millennium Island from the capital, South Tarawa,[18] accompanied by approximately 25 journalists.

The celebration, which was broadcast worldwide by satellite, had an estimated audience size of as many as one billion viewers.