# Millennium, again

I know you are probably sick of it, but regarding when the millennium
occurs, here, I think, is the interesting question-
What was the date exactly 1000 years before January 1, 2000 (or, January 1,
2001)?

Isn’t it a fact that in either case, it was not January 1, 1000 (or, January
1, 1001)?

That is, with the change in the Gregorian calendar in the 1500s, either date
(1/1/2000, or 1/1/2001) will not be the end of 1000 years from the date
1/1/1000 (or 1/1/1001)

Therefore, what is going on here?

Yes, you are 100% correct. From 1/1/1001 to 1/1/2001 is slightly shorter than a thousand years. The difference being about a week and a half resulting from the switch from Julian to Gregorian calendars.

Similarly, the elapsed time from 1/1/1 to 1/1/1001 was about a week longer than one thousand revolutions of the earth around the sun. This is because the Julian calendar calculated a year at 365.25 days, when the correct figure is closer to 365.24 days.

On the other hand, the duration from any New Year’s Day to the next is either (1/4 day) shorter or (3/4 day) longer than a real year.

And let’s not forget, 1/1/1 didn’t really exist, because the Christian calendar wasn’t invented until a few hundred years later.

Anyone want to discuss the ramification resulting from the change of New Year’s Day from March 23 to January 1? No? Neither do I.

The bottom line is that the only siginificance to this coming January First is that we change all four digits when we write the date, and that is some kind of culture shock. Don’t get so anal about it.

Whoa. January 1, 1001 to January 1, 2001 will be nearly exactly a thousand years (ignoring the fraction of a day that even the Gregorian calendar doesn’t handle). The point to the shift to Gregorian and the loss of the ten days was to bring the calendar back into whack with the true length of the year, the Julian calendar having ran over by 0.75 days per century. The ten-day skip took into account the time since the Julian calendar was instituted in the 1st century BC. So December 27, 1000 A.D. (999 years ago yesterday) was exactly 1000 years before January 1, 2001, taking both the Julian-to-Gregorian shift and the error in the Julian “year” into account.

Also, I have to differ with Keeves. Granted that Augustus did not make a diary entry: “January 1, 1 A.D. According to Virgil’s Eclogues, today marks the naming-day of the Universal Savior.” (in Latin, of course) However, and taking into account the goofy count-backwards-from-the-kalends Roman day-numbering system, Augustus might well have dated something as the first day (kalends) of January in 753 A.U.C., which would equate to 1 A.D. or C.E. by later epochal systems. (Note that half his empire would have wondered what the heck A.U.C. was, since they used the Seleucid Era for the year number.)

Whoa. January 1, 1001 to January 1, 2001 will be nearly exactly a thousand years (ignoring the fraction of a day that even the Gregorian calendar doesn’t handle). The point to the shift to Gregorian and the loss of the ten days was to bring the calendar back into whack with the true length of the year, the Julian calendar having ran over by 0.75 days per century. The ten-day skip took into account the time since the Julian calendar was instituted in the 1st century BC. So December 27, 1000 A.D. (999 years ago yesterday) was exactly 1000 years before January 1, 2001, taking both the Julian-to-Gregorian shift and the error in the Julian “year” into account.

Also, I have to differ with Keeves. Granted that Augustus did not make a diary entry: “January 1, 1 A.D. According to Virgil’s Eclogues, today marks the naming-day of the Universal Savior.” (in Latin, of course) However, and taking into account the goofy count-backwards-from-the-kalends Roman day-numbering system, Augustus might well have dated something as the first day (kalends) of January in 753 A.U.C., which would equate to 1 A.D. or C.E. by later epochal systems. (Note that half his empire would have wondered what the heck A.U.C. was, since they used the Seleucid Era for the year number.)

Under the Julian calendar, each 400 years had 300 regular years (109500 days) and 100 leap years (36600 days), for a total of 146100 days, averaging 365.25 days per year.

Under the Gregorian calendar, each 400 years had 303 regular years (110595 days) and 97 leap years (35502 days), for a total of 146097 days, averaging 365.2425 days per year.

In the paragraphs below, I will refer to this duration (365.2425 days) as a “standard” year. One thousand such years would be 365242.5 days.

The 1000 years from Julian 1/1/1 to Julian 1/1/1000 contained 750 regular years (273750 days) and 250 leap years (91500 days), totalling 365250 days, which is 7.5 days more than a thousand standard years.

A few centuries later, that 7.5 day error had grown to eleven days, which Pope Gregory deleted from the calendar. Therefore, although Julian 1/1/1001 to Julian 1/1/2001 would have also been 365250 days, the convention is to count these thousand years as running from Julian 1/1/1001 to Gregorian 1/1/2001 (or a year earlier than each).

That time comes to eleven days less than 365250 days, and deduct three more days for the lack of leap years in 1700, 1800, and 1900. This comes to 365236 days, which is a full two weeks shorter than a thousand standard years.

But in the long run, Gregory’s “Century Leap Year Rule” does average out in the long run. Add the two millennia together, and there have been 730486 days from Julian 1/1/1 to Gregorian 1/1/2001, which is only one day longer than 2000 standard years, and that one day will be compensated for by the lack of a leap day in 2100 and 2200.

Well, if those medieval people had had the good sense to invent the Gregorian Calendar back in 1000 A.D., it would be exactly 1000 years from 1-Jan-1000 A.D. to 1-Jan-2000 A.D…

(Except for that pesky one-day-in-30000-years correction factor the Gregorian Calendar fails to take into account.)

The truth, as always, is more complicated than that.