Does the new decade start the day after tomorrow, or at the end of 2010?

It’s at the end of 2009 without question. It started Jan 1st 2000, and it ends Dec 31 2009. That’s ten years, that’s the decade.

you count from zero (nothing) to 9 then start the next group so 2010 is in the next decade

The milennium started in 2001, the new decade begins in 2011.

@stranger_in_a_strange_land That’s what my dad says. Why wouldn’t the milennium start in 2000?

2000 was the last year of the second milenium. Just like 1900 was the last year of the 19th century. Remember there was no year zero when the calendar was retroactively created in the fourth century.

@stranger_in_a_strange_land : technically, you’re correct, but it’s easier to think that the decade begins in 2010 just like it’s easier to think that the millenium began in 2000, and I’m all for easy.

@hawaii_jake I totally agree with you.

The new decade begins on January 1, 2010. The last decade ended on Dec. 31, 1999. 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 ~ count them. That’s ten years. It’s the same thing with your birthday. We say someone turns 16 on their 16th birthday, but they’re actually completing their 16th year, and the day after their birthday is the first day of their 17th year on the planet. When they’ve completed it and their birthday comes round again, they’ll be called 17, when in reality, they’ve begun their 18th year, etc.

A decade is 10 years. It could start in 2013 or 2019 if we wanted to count that way.

99.9% of us are happy to count the next decade from January 1, 2010.

The key here, as @stranger_in_a_strange_land points out, is that there was no year zero. A decade is ten years. The first decade A.D. was 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, because there was no zero. So the second decade was 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and this decade is 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010. The new decade does not begin until January 1, 2011. Otherwise some decade somewhere has to get short changed by a year. Now you can describe the decade that began January 1, 2000 and ends December 31, 2009, and it is indeed a decade, but it is not the 202nd decade, because it has no relationship to earlier decades. I could just as well call the ten years from my 1st birthday to my 11th a decade, but it’s not meaningful to call it the decade.

If you don’t want the correct answer, why ask?

It can really go either way. Ten years is a decade. You can start counting wherever you like. You can say that the 1960s was a decade, meaning Jan. 1960— Jan 1970, or you can say Dec. 1960— Dec. 1970.

This is a simple concept gone terribly astray. A decade is 10 years, as counted 1 – 10. A full year lasts from January 1 – December 31. Thus the last year of the 201st decade is the end of 2010, not the beginning. From your birth until the first anniversary is year ONE! It can be complex because there are so many ways to measure a year.

To list the end of the decade as the first day of the 10th year instead of the last day, is to forget what the dec- in decade stands for; Base 10 or 1 -10, not 0 – 9!

No way. If you think that you also must think that on the day of your birth, your age was “one”. You became ten after living ten years, just as a period of time becomes a decade after the passing of ten years, starting with one at the end of the first year.