That out of the way, let's go on to talk of many things: shoes, ships, sealing . . . --- wait, no.
What about these different calendars used around the world? Some countries use our calendar and also refer to other ones too. Japan counts years by length of the emperor's reign and is now in the year of Hisei 12, the 12th year of the reign of Akihita.
The year 2000 is 5760/5761 on the Jewish calendar; and in Israel, religious authorities are against celebrations of the Christian New Year in general, and December 31, 1999 falls on the Jewish Sabbath.
The year 2000 is 1420/1421 on the Islamic calendar, and in China it will be 4698.
Then there is the problem with the monk who first worked this out making a little error of apparently about four years. So, technically, it's not really the 2000th birthday of Christ.
Also, what started out as a Christian calendar has gradually evolved into a secular one with "holy days" giving way to "holidays" and "Sabbaths" losing out to "weekends". Even the "holidays" are conveniently celebrated on Monday instead of the correct date.
Oh well.
For people who are wondering about the new millennium starting on January 1, 2001, you have to remember that the calendar started with the year "1", not the year "0". Back to that poor monk again. Supposedly he was using Roman numerals and they don't have a "0".
Are you buying all this stuff about that monk? Doesn't it sound like the sort of thing you use after a former employee has left the company to go on to bigger and better things?
Then, who knows? Maybe this guy was the original patron saint of some programmers.