# "2020s" = 2020-2029 or 2021-2030?

When I define a decade, it contains 10 years, starting from '1 and ending on '0.

Specifically, I mean by '1-'9 being 1st-9th and '0 being 10th.

Since the current decade, namely the 2010s, ranging from 2011 to 2020, is about to end.

One time me and some other users were having a conversation on MSE about how the decades are being ordered.

I understand what User45266 is saying, since saying "the 30s" and including 40 (?!) is not very logical. But (strictly speaking) it is '1-'2-'3-'4-'5-'6-'7-'8-'9-'0, not '0-'1-'2-'3-'4-'5-'6-'7-'8-'9. For '0 to be the 1st year of the decade there would have to be a "year 0" (?) and there isn't in the common sense.

Did the 2010s already end? Or is it still in progress (but about to end)? Does the 2020s contain the years 2021-2030 or 2020-2029?

• The word "decade" can be used refer to a ten-year period with any starting point: e.g. in 2027, it will be possible to say "It has been a decade since 2017". By analogy with the usage with centuries, the time period from the start of 2011 to the start of 2021 could be referred to as the "202nd decade". Commented May 5, 2020 at 7:00
• Since AD1 (or 1CE) is the first year, every decade and every century should end with a zero. But in common parlance the forties, e.g., begins in 1940 and ends with 1949. The turn of the century was celebrated as the calendar turned to 2000. That’s the culture. Commented May 5, 2020 at 7:39
• Technically, this is a sort of "fencepost problem" involving "counting from zero". A discussion of it Is found here: forum.gcaptain.com/t/…. Because of its hackish nature, it might have great success (or possibly a previous answer) on one of the number or computacional Stacks. Commented May 5, 2020 at 8:10
• You started the question by saying, "when I define a decade." If that's how you've defined it, then that's what it means to you. Commented May 5, 2020 at 15:54
• Does this answer your question? Does the nth century contain the (100n)th year? Commented May 5, 2020 at 15:57