I always appreciated that the years of X emperor’s always increased. Imagine how confusing would it be to have the chaos years as 6,4,5 or 5,4,6.

Explanation: In 69 AD (nice), a series of four Emperors ruled, one after another. Galba, having overthrown Nero in 68 AD, was himself overthrown by Otho. Otho, then, was overthrown by Vitellius. The general Vespasian sent his son to pledge allegiance to Galba and assure Galba and the Senate that Vespasian had no designs on anything except his assigned duties crushing a rebellion in Iudea. Vespasian’s son, however, arrived to find he was two Emperors late to pledge allegiance to Galba, and rode back to tell his dad that things were fucked - Vespasian then marched on Rome and overthrew Vitellius, managing a stable rule for the next decade. Hell of a year!