Compilation of the chronicle now known as the 'Annals of Ulster' (which covers the period 431-1540) was begun in the late fifteenth century, under the direction of one Cathal Óg Mac Maghnusa, who died of smallpox in 1498. Up to 1489, the original compilation was the work of a single scribe - Ruaidhri Ó Luinín. Other hands have made additions in margins and spaces. Although many of the earlier entries are in Latin, and Latin words and phrases continue to be used later, the evolution of the Irish language, from Old through Middle to Early Modern, is apparent in the work. Research (Daniel P. Mc Carthy, Trinity College, Dublin) has shown that, up to the annal 1012, the convention of beginning the year on the feast of the Annunciation (25th March following the 1st of January when the year is now said to start) is followed. For the modern reader, this has the effect of attributing an annal to the year before that which was intended. The dates quoted on this website have been corrected into modern usage.