At the end of HB 31 we have the following:
“When Gratian ruled for the second time with Equitius, the Saxons were received by Vortigern, 347 years after the Passion of Christ.”
The consulships of Gratian were:
|Year||Consul prior||Consul posterior|
|371||Flavius Gratianus Augustus II||Sextus Claudius Petronius Probus|
|374||Flavius Gratianus Augustus III||Flavius Equitius|
How did this incorrect dating for the Advenrtus come about. There are two possible explanations:
1. It has already been shown how the error of Vortigern’s reign starting in the year 390 AD came to occur, see Vortigern to Badon in the Red Book of Hergest. This would have implied an Adventus in 393 AD, that is 366 AP. If it was later assumed that 366 was in anno domini dating, then the notion would have occurred it was during the consulship of Gratian.
The inclusion of Equitius was an error as can be seen by the HB claiming it was Gratian”s second consulship, rather than his third. As it turns out, the reference was to Gratian’s first period as consul.
2. Alternatively, again using the 393 AD date for the Adventus, if this event was placed one Metonic cycle too early it would result in the date 374 which is indeed the year of the consulship of Gratian and Equitius.