When Does the New Decade Start? 2020 or 2021?

[Guest]

Hello, I'm not great at maths but i'm trying to think this so i really appreciate your help

There is a period of time between this exact moment and the beginning of year 1 AC: this period of time is one year, in fact lim(t–>1) t = 1.
From this moment to the beginning of the second year there is another period that lasts one year, in fact [lim(t–>2) t] - 1 = 1 and so on… Then the time to get from the point that we put as 0 to the 10th year is exactly 10 years, and at the year number 10 one decade (that is by definition a period of 10 years) has passed. So this is the first dacade and so passes the first century, the first millennium and so on until the millennium 3, century 1, decade 2, year 9, a.k.a. 2019. Between the year 9 and the year 10 there is of course a period of 1 year… so, as done before, {[lim(t–>2020) t] - 1} + 1 = 2020 that is the beginning of the millennium3, century 1, decade 3.

[Baltuilhe]

Good afternoon!

Century
1 to 100 --> 1st century
101 to 200 --> 2nd century...
so...
2001 to 2100 --> 21st century, ok?

To discover the century find the 'next' year that ends by '00'. This year is the 'name' of the century.

So... 3235 --> next year --> 3300, right? So 33rd century

Same to millenium!

1 to 1000 --> 1st millenium
1001 to 2000 --> 2nd millenium
2001 to 3000 --> 3rd millenium.

Well, for decades the pattern is similar.

2001 to 2010 is the 1st decade (of 21st century)
2011 to 2020 is the 2nd decade...
..

2091 to 2100 is the 10th decade

ok?

Differently, we had the sixties, seventies, ... these years were :
sixties: 1960 till 1969
seventies: 1970 till 1979

ok?

Hope i could help!

[Guest]

Alright, I got your point. You are basically saying: if I count from A to B, then the next number has to be C (that is, if I count from 1 to 100 which is the first century, then I must state that the second century starts in 101 and ends in 200 and so on, so that the 3rd decade of this millennium starts in 2021 and ends in 2030; this is made assuming that 0 is not a natural number). What I am saying is that in real numbers (or any set that countains them) there is no way you can count, because between two numbers there is an infinity of numbers. Also, the year 0 happens to be the chosen beginning. In the exact moment one decade passes, the next decade starts. Then the first decade starts at 0 and ends at 10, and at 10 (or better, at lim(t–>10+) t =10,), idem works for the second decade, that starts at 10 and ends at 20 (or better, at lim(t–>20+) t = 20)… so you go from 2000 to 2010, from 2010 to 2020, from 2020 to 2030 and so on. I don’t know how much you know about limits, some notions can be helpful

[Guest]

Didn't we have this same argument in 1999? Was the first year of the new millenium 2000 or 2001?

That was an extremely important question- when should we celebrate, Dec 31, 1999 and Jan 1, 2000 or Dec 31 2000 and Jan 1 2001? My solution was to start celebrating Dec 31, 1999 and continue until Jan 1,2001!

(So they all got blind drunk
Which completed their bliss
And we keep up the practice
From that day to this!

"The birthday of St. Patrick" Leo MacCaffrey)

[rafaelsanc]

Thank you so much for the details. I'm really glad to know more about it.

[Raiden Mitchell]

The new decade began on January 1st, 2020. It seems so to me.

[Guest]

I remember having this argument in 1999! When did the new millenium start, in 2000 or 2001?

There was no "year 0" The first decade started Jan. 1, 1 AD and ended 10 years later on Dec 31, 10 AD. The second decade started Jan. 1, 11 AD.

The first century started on Jan. 1, 1 AD and ended 100 years later on Dec 31, 100 AD. The second century started Jan. 1, 101 AD.

The first millenium started on Jan. 1, 1 AD and ended 1000 years later, on Dec 31, 1000 AD. The second millenium started Jan. 1, 1001,

My suggestion was that we start the party on Jan, 1, 2000 and end it on Jan, 1 2001, Of course, I was younger then!