29 October 878 AD: A celestial  phenomenon was observed in Ireland on this day.

A solar eclipse on the fourth of the Kalends of November [29 October] the twenty-eighth of the moon, on the fourth feria, about the seventh hour of daylight, fifteen solar days having intervened.

The Annals of Ulster 

This celestial phenomenon was seen as a total eclipse in central and northern Scotland and as a deep eclipse in all of Ireland as well as in parts of England and Wales. It was also recorded in the Anglo-Saxon Chronicle, the Regino of Prüm, and annals from Iceland and Fulda in Germany, of which only the last compare with the Annals of Ulster record for accuracy.

The sun rose totally eclipsed in 73° N. and 42° 8′ W. at about 9.53 local time, and the central line of the eclipse, after passing near Dublin, Aberystwyth [Wales], Dover [England] and Fulda [Germany], went off the earth at sunset, about 130 miles south of Moscow [Russia] at 4.20 local time; St. David’s, Winchester and London were within the limits of totality. 

The Irish monks of ancient Ireland contained amongst their ranks not just scribes but also astronomers. They scanned the skies to record what they saw, not just so they could calculate the correct day to celebrate Easter according to the phases of the Moon but also for such signs or portents heralding the coming of the ‘Last Days’ as disclosed in the Biblical Book of Revelations.