The start of the 3rd millennium
It is a popular and persistent misconception that the year 2000 AD was the
first year of the third millennium.
This is not true: 2000 AD was the last year of the second millennium,
and 2001 is the first year of the third millennium.
This can be seen easily as follows:
there has never been a year 0 (zero)
==> the first year of the 1st century AD was the year 1 AD
a century has 100 years
==> the 1st century ended with the year 100 AD
==> the year 101 AD was the first year of the 2nd century
... ... etc.
==> 1901 AD was the first year of the 20th century
==> the year 2000 AD is the last year of the 20th century
The 21st century, and thus the 3rd millennium,
started with the year 2001 AD !!
In what we now call the 6th century, the then Pope gave Dionysius Exiguus
(= "the Little") the task to compute when Christ was born, using
available archive material. Dionysius did not take Christ's birth date
itself, but the day of his circumcision -- which took place at the 8th day
after birth -- as the first day of the year 1 AD, not 0 (zero).
This is contrary to our current usage of starting at zero years when a
child is born: a child is 1 year old when it has lived for one year.
For Jesus this is not the case.
The reason for this difference is that Dionysius did not know the number
zero; the zero was introduced in Europe only several centuries later.
Hence, when Christ was one year old the year 2 AD started, etc.
Consequently, at the beginning of the year 2000 Christ, if still alive,
would be 1999 years old.
And therefore two millennia have past since Christs birth at the end of
2000; after all a millennium is per definition exactly 1000 years long.
That Dionysius named the day of Christ's circumcision the first day of
the year, 1 January, means that Christ's birth was to be celebrated
on 25 December -- now known as Christmas Day.
The year before 1 (=1 AD) is -1 (= 1 BC), since there is no
The first century BC thus started in the year 100 BC and ended in 1 BC.
Confusingly, in some astronomical calendars the year before 1 AD
is called 0 (zero), and in that case the year -1 is 2 BC.
Dionysius Exiguus made another mistake: he mis-computed Christs birth
by about five years. Most likely the Star of Bethlehem was the star
DO Aquilae, now a faint star in telescopes, but in 5 BC easily
visible for about 70 days because it underwent a supernova explosion.
[see, for example, The Star of Bethlehem: An Astronomer's View
from Mark Kidger].
For background info on calendars, see e.g.:
"Calendars" by L.E.
Doggett or the
Calender Zone web site.
An excellent account of Dionysius Exiguus and the absence of the number
zero, can found in the book
Zero, the biography of a dangerous idea by Charles Seife
(Penguin Books, 2000).
Voor een uitgebreid overzicht over de wettelijke tijdregelening in
Nederland, zie deze
Robert van Gent (Dutch only).
Counting the days ...
Until the beginning of 2001 this page contained a counter that showed the
time left before the start of the 3rd millennium.
Now that the 3rd millennium has started,
this page gives the time passed since that millennium started.
If your browser:
how many days, hours, minutes and seconds have passed since the
start of the 3rd millennium;
empty form fields; sorry about that.
The above time information is only correct if your computer system clock
is set at the correct time.
The time counter may be off by one hour in daylight saving time periods;
I do not know how to check (and correct) for this -- sorry.
Leap seconds are now and then introduced to compensate for the
gradual slowing down of the Earth's rotation: an extra second
23:59:60 is inserted between 23:59:59 and 24:00:00, e.g.
at New Years Eve.
At the moment the daily variation of the Earth's rotation is 0.002 sec,
which means that after about 500 days there is 1 second difference, so
an update of the so-called Universal Time (UT) is needed about every
one and a half year, the result being the Universal Time Coordinated (UTC).
There is no need to account for leap seconds in the counters here,
as the counter follows the computer system clock, and that clock should
be properly updated.
This is the first, and so far only, Web page I made with a
And it satisfies the
Jos van Geffen --
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created: 5 January 1999
last modified: 30 September 2010