If you wanted to design the perfect place to observe UTC+0, you could not do much better than Sao Tome and Principe.

The island of Sao Tome sits at approximately 0.3 degrees North latitude and 6.7 degrees East longitude: nearly exactly at the intersection of the Prime Meridian (0 degrees longitude) and the Equator. This is the mathematical origin point of the geographic coordinate system that organizes the entire planet’s maps and timezones.

The timezone here is Africa/Sao_Tome: UTC+0, year-round, no daylight saving.

The coordinates of origin

The Prime Meridian, 0 degrees longitude, was fixed at the Greenwich Observatory in London by international agreement in 1884, at the International Meridian Conference in Washington. It runs south through Africa, crosses the Gulf of Guinea, and passes a few kilometers east of Sao Tome island.

The Equator, 0 degrees latitude, passes through the northern part of the island of Principe and close to Sao Tome.

The island of Ilheu das Rolas, just south of Sao Tome and part of the same country, contains an equatorial monument marking the 0-degree latitude line. Standing on it, you are at the intersection of the two defining lines of Earth’s coordinate system.

The geographic coordinate (0,0), sometimes called Null Island in informal usage, is in fact located in the open ocean of the Gulf of Guinea, a few hundred kilometers from Sao Tome. But Sao Tome is the inhabited land closest to this geometric origin point.

UTC+0 by geography

Solar noon at Sao Tome occurs around 12:27 local time (UTC+0), since the island is east of the Prime Meridian by about 6.7 degrees. This is a close match. UTC+0 is essentially correct for Sao Tome’s longitude, confirmed by its near-zero position on the coordinate grid.

The island is on the equator, so day length varies only slightly year-round. There is no practical argument for daylight saving time.

The Portuguese cocoa islands

Sao Tome and Principe was uninhabited when the Portuguese arrived in the 15th century. The Portuguese established the islands as a center for sugar production, then later cocoa, using enslaved labor from the African continent. By the 19th century, Sao Tome and Principe was producing a significant fraction of the world’s cocoa.

The islands gained independence from Portugal in 1975. Today they produce small quantities of high-quality cocoa still sold under the islands’ name.

In 1997, Sao Tome shifted briefly to UTC+1 for a period before returning to UTC+0 in 2018. This transition is recorded in the IANA database and can affect historical timestamp handling.

For developers

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