On December 23
No pivotal events are recorded on exactly December 23 — the closest is Charlemagne crowned Emperor of the Romans on December 25, 800 CE (2 days later).
This week in history (Dec 20 – Dec 26)
On Christmas Day 800, during Mass at St Peter's Basilica in Rome, Pope Leo III crowned the Frankish king Charlemagne 'Emperor of the Romans' (Imperator Romanorum).
On 26 December 2004 a magnitude 9.1-9.3 megathrust earthquake ruptured the seafloor off the west coast of northern Sumatra, Indonesia, where the India Plate subducts beneath the Burma Plate.
21 December 2015SpaceX lands an orbital rocket booster, opening the reusable-rocket eraScience, technology & invention
On 21 December 2015, the private American company SpaceX landed the first stage of its Falcon 9 rocket vertically at Cape Canaveral, Florida, after the booster had helped deliver eleven Orbcomm communications satellites to orbit.