Rather more precise dating for the war is given in The Annals of Aman (in volume X of The History of Middle-earth). Reckoned in Valian Years (which are somewhat longer than solar years), and counting from the first blooming of the Two Trees of Valinor, the war is said to have begun in 1090. After two (Valian) Years of war, the Valar fought their way to Utumno and besieged it until 1099, when the fortress fell and Melkor was captured, bringing the war to its end.

Converting from Valian Years to solar years is not straightforward (and in fact there are various different approaches) but it is possible to produce some estimates using a typical calculation. In solar years, this would mean that the War of the Powers began 10,445 years after the beginning of the Years of the Trees, and lasted for eighty-six years, with the long siege of Utumno occupying sixty-seven of these. By this system, the war ended 3,843 years before the beginning of the Years of the Sun.

It should be noted that the name 'Great War of the Gods' only appears in The Annals of Aman (ibid) and so cannot be considered strictly canonical. In the same source, the War of the Powers is also described as the 'war of the West upon the North' (referring to the Uttermost West as the home of the Valar, and the far North as the ancient domain of Melkor).