29 October 878 AD: 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 878 AD
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, Regino of Prüm, and annals from Iceland and Fulda in Germany, of which only the last compare with these Annals of Ulster record for accuracy.
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 Book of Revelations.
And I beheld when He had opened the 'SIXTH SEAL,' and, lo, there was an earthquake: and the sun became black as sackcloth of hair, and the moon became as blood... And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bond man, and every free man, hid themselves in the dens and in the rocks of the mountains; and said to the mountains and rocks, FALL ON US, and HIDE US from the face of Him that sitteth on the Throne, and from the WRATH OF THE LAMB: for the great day of HIS WRATH is come; and who shall be able to stand?