Founding of Cluny Abbey
An abbey answerable only to the pope will lead church reform

In 910 Duke William the Pious of Aquitaine founded the abbey of Cluny in Burgundy and placed it directly under the pope, free of lords and bishops. Cluny became the centre of church reform, and its abbey church was the largest in Christendom until the 16th century.
Wikipedia (Russian) · Wikipedia (English) · 10th century
Meanwhile around the world (±25 years)
Africa
- c. 900 The bronzes of Igbo-Ukwu — 10 years earlier
- 909 Proclamation of the Fatimid Caliphate — 1 year earlier
Asia
- 907 Fall of the Tang dynasty — 3 years earlier
Americas
- c. 900 Rise of Chichen Itza — 10 years earlier
Alive at the time
- Oleg the Wise (aged 65)
- Al-Farabi (aged 38)
- Igor of Kiev (aged 32)
- Æthelstan (aged 16)
- Abu al-Hasan al-Ash'ari (aged 37)
- Edward the Elder (aged 36)