Ceasar Augustus (Luke 2:1)

Good question.  I had forgotten exactly how this all matched up, so looked it up in Eureka:

“The twelve Cæsars” (Rev. 12:1):

1. Augustus Cæsar—Christ born (Luke 2:17).
2. Tiberius Cæsar—John the Baptist (Luke 3:1 2).
3. Caligula—Acts of the Apostles.
4. Claudius Cæsar—Famine (Acts 11:28).
5. Nero—Paul suffered death.
6. Galba.
7. Otho
  8. Vitellius.
9. Vespasian.
10. Titus—Destroyed Jerusalem (Luke 21).
11. Domitian—John banished to Patmos.
12. Nerva—John recalled from exile.

They saw a very remarkable change of times. The previous fifteen years of misrule and cruelty were immediately succeeded by a mild and beneficent reign of sixteen months and eight days. This was the short, but brilliant reign of Nerva, which was inaugurated by an act of the Roman Senate, which condemned Domitian’s memory, and rescinded his decrees. Nerva was one of the best monarchs permitted by the Lamb to occupy the Dragon throne. Under his mild administration of the laws, the people of the Roman Horse was everywhere contented and happy. He extended his clemency as “the minister of the Deity for good” to all who were imprisoned for treason; called home all that had been banished in Domitian’s time, except the tyrant’s own niece, Domitilla, whose freedman had assassinated him; restored all sequestrated estates; punished informers, and, to the utmost of his power, redressed the grievances of every description of his subjects. To christadelphians he allowed the freest toleration, not permitting any to persecute either them or the Jews, though the saints were generally regarded as Atheists, having no visible temples, altars, or sacrifice, which the pagans considered as essential to a profession of religion.
                 -Eureka: An exposition of the Apocalypse

So John saw the things that would shortly come to pass, and Nerva was at the start of that first Seal