Nope, and let me explain.

Let's go back about 1,500 years to Rome, where a monk named Dionysius Exiguus is becoming famous for his translations of ancient works.

Rome in this time is a pretty chaotic place. There's rampaging armies, squabbling churches and economic calamity in a place that used to be the center of the (Western) world. Amid all the confusion, Dionysius wakes up one day and realizes — everyone's forgotten the apocalypse!

You see, most Christians at that time used a dating system known as Anno Mundi (after Creation) that counted the years since the "creation of the Earth." It's a system that has its roots in Jewish tradition — for example, we're in the Hebrew year 5774 until September and Rosh Hashanah (aka Jewish New Year).

In Dionysius' time, almost every Christian Church and sect counted Anno Mundi differently — there's a funny scene about this in the alternate history book Lest Darkness Fall — but most of them believed that the Earth had been created about 5500 BC, making 525 AD their 6025 AM. The popular presumption was that Jesus would return to Earth and send everyone to heaven at 500 AD (6000 AM).

By Dionysius' time, it was pretty clear that the world hadn't ended, which meant there needed to be a new system. Dionysius was also motivated by another dating system used in his time.

Most Roman documents indicate years by saying the "Xth year in the reign of Consul X." While some documents refer to years since the founding of Rome (Ab urbe condita), this isn't as common as the consular dating.

One of the big things Dionysius (and other Christians) needed to determine was the date of Easter each year. Churches would publish Easter tables indicating these dates, and the Church of Alexandria's was one of the better-known ones. Problem was, Alexandria used a dating system based on years since Diocletian began ruling Rome (Nov. 20, 284).

Dionysius thought this was bullshit. Diocletian persecuted Christians, so why should the Christian calendar honor him?

Instead, he came up with a listing of Easter tables based on years since the Incarnation of Jesus, which he said was 525 years ago. (Now, we think he could've been as much as five years off.)

Dionysius' ideas took a while to take off. As we know, there were a lot of competing ideas circulating in Rome, and Dionysius' was just one. It survived his death, however, and got a huge boost when the Venerable Bede used it enthusiastically in his Ecclesiastical History of the English People.

Charlemagne, who devoured Bede (No, not literally.) was an enthusiastic convert and took up Dionysius' system. The rest, as they say, is history ...

But wait! What about the rest of the world?

The Chinese (Han) Calendar uses a lunar system instead of a solar one, and has a different start year to boot. In 1912, however, Sun Yat-Sen decreed that Shíyīyuè 13th 4609 of Huángdì Era was the first year of the Republic of China. After the Chinese Civil War, the People's Republic of China continued to use the Gregorian Calendar and dating system.

In Islamic tradition, years are counted since the Hegira (622 AD), when Muhammed and his followers fled Mecca to Medina.

And as above, the Hebrew calendar continues to use a different numeral system.

There's also the Mayan calendar and all kinds of other systems ...

And if you want more, check out the FAQ page on this very question.

No. Here's the FAQ on the topic; the "best answer" link there gives all the information you're after.

Normally I'd say "there's always room for people to contribute new answers on this topic", but in this case the threads in the FAQ cover the subject very thoroughly.