Instead of 1700s? I guess it’s just a traditional thing to say? (Some people will say 1700s but it’s not very common)
Does this also happen in languages such as Chinese, Japanese, etc.?
Because the 1700s were the 18th Century. Nobody says ‘the 2000s’. We say it’s the 21st Century.
EDIT: I may have been English-speaking-centric there. If you’re asking specifically about other languages, I don’t know.
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we say the 20s, 30s. etc. We don’t say 3rd decade, 4th decade, etc. So why the difference?
We say somebody is in their fourth decade, don’t we?
I don’t. I say they’re in their thirties.
It’s just how everyone counts:
1-100 – the first century
101-200 – the second century
201 -300 – the third century.
Note that other than the last year of the century, the numbers are one less than the century number. Thus, the date 123 is in the second century. Because the first century consisted of dates below 100, the century number is one greater than the first numbers in the date.
Yes I know that is how it is counted. But why not say the perfectly valid term 1700s?
People use 1700’s all the time - it is not at all rare. They’re completely interchangeable and it’s quite handy if you end up in one of those long, dry academic sentences where the term 18th century comes up three times. You can mix in a ‘1700s’ to make it sound less awkward.
Now if the question is why not always use 1700’s and ditch 18th century, I’d guess I’d turn it around and ask why should we :)?
Is it Twelve Forty-Five or Quarter to One?
Bacause people still knew how to count back then. But with the third millenium, they got confused. How many people you know celebrated the TM on January 1, 2000?
Pick ONE, damnit!!!
Exactly.
I teach college history, and a couple of my courses deal with this time period. I switch back and forth between “1700s” and “18th century” mainly so that my lectures don’t sound too repetitive.
I should note, by the way, that a certain percentage of my students never grasp the concept. Even after i explain how it works, i still have some students who think that the 18th century is the 1800s, and so on.
I grew up in the 1980s, when digital watches were increasingly popular. There was a popular radio DJ in Sydney who used to announce the time by saying, “The time is a quarter to one, or twelve forty-five for the digitally-educated.”
We have different ways of saying the same thing to keep speech and the written word from getting boring.
If you want to use the same terms in an unvarying way, then that would be like reading a novel written with all the panache of computer code.
Some do, when they mean the decade that followed the '90s.
To those who say " It’s a quarter of one," I reply, “What? It’s twenty-five hundredths?!?”
Is it 3:34, or 3:35, or 25, or 6 to 4?
I see what you did there. 
Well, French labels centuries in the way you hate, except that they put the numbers in Roman numerals. So they would write, the “XVIIIth century.” The other possibility you mention is one of those things that’s just not done.
In Italian, though, they do use the 1X00’s convention, except that they elide that “1,” meaning that that you would prefer to call the 1500’s, and what the French would call the XVI[SUP]e[/SUP] siècle, they call the 500’s.
So that is why the Italian film 1900 (by Bernardo Bertolucci) has the Italian title Novecento.
In Spanish, the main naming patter is to use “el siglo ___” followed by the cardinal number in speech, but the more formal ordinal number in writing. The 1900s are “el siglo veinte” (“the century twenty”) in regular conversation or in informal writing, but “el siglo vigésimo” in more formal use.
I would generally assume 1900s refers, first and foremost, to 1900-1909.