How Did We Get our Calendar?

Many scholars date the birth of Jesus Christ at 4 BC. There are very good reasons that this is a good date for this event, however, you, like me, might be wondering something. Doesn't "BC" stand for "Before Christ"? Well, yes, it does. So how in the world could Jesus Christ be born 4 years before... Himself?

This is a good question. It is because of an error that an astronomer (Dionysius Exiguus, AD 470-544, Rome, Italy) made in calculating Jesus' birth. How did we get our calendar in the first place? I'll sum up as best I can:

• In 45 BC, Julius Caesar got Sosigenes, an Alexandrian astronomer, to correct the calendar because of the errors from years of intercalation. What is intercalation? It is when days are added to the calendar to keep the months and seasons synchronized. It is used to correct drift over time. Of course, Sosigenes didn't know it was 45 BC. Instead, he used 709 AUC. "AUC" stands for "ab urbe condita," meaning, "from the foundation of the city" [of Rome]. The leap year was instituted, and the Julian Calendar was born. The month Julius (our July) was named after Caesar himself. The month Augustus (our August) was named after Caesar Augustus.
• In AD 525, Pope John I commissioned Dionysius Exiguus to Christianize the Julian Calendar because he saw it as improper to account time by a calendar created by a nation that had persecuted Christians. He determined December 25th, 753 AUC to be the birth of Christ and declared 754 AUC to be "anno Domini 1," or "the year of our Lord 1"; thus AD 1.
• In AD 1582, Pope Gregory XIII made a decree for Christopher Clavius to make adjustments in the calendar because it was drifting off the seasons. This is because, technically, the Julian calendar had leap years, but that wasn't enough adjustment. Its years were exactly 365 days and 6 hours long (365.25). An actual solar year is 365 days, 5 hours, 48 minutes and 46 seconds long, so the Julian calendar was 11 minutes, 14 seconds too long. This doesn't sound like much, but it caused seasons to drift off with the months. His decree was that Thursday, October 4, 1582 (Julian) plus one day would be Friday, October 15, 1582 (Gregorian). So, 10 days were skipped! He made further adjustments to the leap year rule as well. He said if a year is a century year (i.e. AD 1600, 1700, 1800, 1900, 2000, etc.) and if it is divisible by 400 with no remainder, it is to be a leap year, otherwise, it is not. Thus, AD 1600 was a leap year but AD 1700, 1800 and 1900 were not. Likewise, in our own lifetime AD 2000 was a leap year because it is exactly divisible by 400.

Virtually everyone before and after Dionysius Exiguus has calculated the birth of Christ to not even be near December 25 time of the year, and also a few years earlier than 753 AUC (or 1 BC, there is no "zero year" on the calendar; i.e. 1 BC + 1 year = AD 1, not 0).

So, we now return to the question: How could Jesus Christ be born 4 years "Before Christ" (4 BC)? Just what error did Dionysius Exiguus make? That is the subject of a future article.