Most historical accounts state that the island was discovered on 21 May 1502 by the Galician navigator João da Nova sailing at the service of Portugal, and that he named it "Santa Helena" after Helena of Constantinople. Another theory holds that the island found by da Nova was actually Tristan da Cunha, 2,430 kilometres (1,510 mi) to the south, and that Saint Helena was discovered by some of the ships attached to the squadron of Estêvão da Gama expedition on 30 July 1503 (as reported in the account of clerk Thomé Lopes). However, a paper published in 2015 reviewed the discovery date and dismissed the 18 August as too late for da Nova to make a discovery and then return to Lisbon by 11 September 1502, whether he sailed from St Helena or Tristan da Cunha. It demonstrates the 21 May is probably a Protestant rather than Catholic or Orthodox feast-day, first quoted in 1596 by Jan Huyghen van Linschoten, who was probably mistaken because the island was discovered several decades before the Reformation and start of Protestantism. The alternative discovery date of 3 May, the Catholic feast-day for the finding of the True Cross by Saint Helena in Jerusalem, quoted by Odoardo Duarte Lopes and Sir Thomas Herbert is suggested as being historically more credible.

What date was the island discovered on?