I notice that we have tags "20th-century" and "1900s"; these would mean the same thing for many (not necessarily most) of us. For others, the alternative numerics (1900s) refers not to a century, but a decade.

General notions of dates/era, etc. are important to our work, so taking a thoughtful approach to tagging would be a good thing for us to do.

From the Wikipedia entry about "Century," I note, "There is no "zeroth century" in between the 1st century BC and the 1st century AD."

From the same source, "Besides the Gregorian calendar, the Julian calendar, the Aztec calendar, and the Hindu calendar have cycles of years that are used to delineate whole time periods; the Hindu calendar, in particular, summarizes its years into groups of 60, while the Aztec calendar considers groups of 52."

The Wikipedia entry talks about "Alternative naming systems," and gives examples of such for, in particular, Sweden, Norway and Finland. Adding, "The same system is used informally in English. For example, the years 1900–1999 are sometimes referred to as the nineteen hundreds (1900s). This is similar to the English decade names (1980s, meaning the years 1980–1989)."

Perhaps others will add more about the possible confusion with "decades."

  • Back at you, @ColeValleyGirl. I would use 1800s to refer to the 19th century. Will updated/edit the question for what may be my contrary understanding.
    – GeneJ
    Commented Nov 22, 2012 at 15:19
  • @ColeValleyGirl, that seems very important. Care to edit/further modify the question, and then convert your comment to an answer in the spirit of discussion?
    – GeneJ
    Commented Nov 22, 2012 at 15:25

4 Answers 4


By 1900s in the question I asked I specifically meant the decade 1900-1910 -- the rest of the twentieth century is irrelevant to that particular question, so I thought 20th-century would be misleading. I also tagged it 1890s because that decade is relevant. I've never used "the 1900s" to mean the 20th century.

I agree we need a standard for tagging for time frames. On reflection, maybe tagging for decades is too granular, particularly if the question title identifies the exact time-frame of interest? If we take that approach, we can use e.g. 18th-century, 19th-century without (much) risk of misunderstanding.

I suspect most of us won't need to distinguish between BC/BCE and AD/CE although kudos to anyone who's taken their ancestry that far back with cited sources :)


After reading the answers here, I tend to agree with ColeValleyGirl. We need standard tagging. Other sites, such as History SE, have also run into this problem. The simplest way to tag it is to use for all centuries and for decades, as needed. If we went ahead and implemented all decade tags now, it would be a mess. To clarify, the tag wiki excerpts usually run like this:

The 20th century began on January 1, 1901, and ended on December 31, 2000.

Referring to the time period between 1930 A.D. and 1939 A.D. by the Gregorian calendar.

Note (per GeneJ's comment); the first decade of a century should have "decade" affixed to it to eliminate confusion

Referring to the time period between 1900 A.D. and 1909 A.D. by the Gregorian calendar.

With this system, almost all questions get a century tag, even if the event doesn't encompass the whole century. So, if a question warrants a decade tag, it should have a century tag also. Keep in mind that tags are used for the purpose of organizing, not defining a question. No organization system will be perfect.

  • 1
    I don't think most question that there would be broad understanding about the term 1930s, but that probably does not translate the same way for the term 1900s. (See Wikipedia, "1900s." en.wikipedia.org/wiki/1900s.) If you opt to go in that direction, then 1900s probably has to be "1900s-(decade)"
    – GeneJ
    Commented Nov 23, 2012 at 22:13
  • Either that or just clarify in the wiki excerpt you get when you hover over the tag. I could be persuaded either way, though.
    – Luke_0
    Commented Nov 23, 2012 at 22:18
  • 1
    If History SE have got a solution, I'm all for borrowing it, with the caveat that @GeneJ made..
    – user104
    Commented Nov 26, 2012 at 11:25
  • Believe you have to add "-decade" to the end of the XXX0s if you want to maintain readability. We simply quote too much work and too frequently utilize the XXX0s as a much shorter reference to the century.
    – GeneJ
    Commented Nov 26, 2012 at 16:53
  • 1
    I would think it is only necessary on "xx00s". There was no "1830s" century.
    – Luke_0
    Commented Nov 26, 2012 at 16:57
  • I agree, Luke, only needed on the XX00 years. (Sorry, I had written XXX0.)
    – GeneJ
    Commented Nov 26, 2012 at 17:33

For the specific case of Gregorian dates, the amiguities cannot be resolved using numerals alone. For instance, is 1900 a year, a decade, or a century?

However, using a wildcard character such as 'x', '?', or '*' can make it more exact. For instance:

1900 - a specific year 190x - a specific decade (1900-1909) 19xx - a specific century (1900-1999)


I believe you're both thinking in Gregorian terms here. If this site were specifically interested in, say, Hindu family history then it would be tagging time frames from an entirely different calendar and those centuries would be meaningless.

I don't see this as a big problem - especially given the relatively small worldwide participation here - but it's worth bearing in mind that there are many different calendars. This is probably more of an issue for representing the data than for asking questions, though, and I did propose a related question somewhere on the old Area51 site.

  • It's like a controlled vocabulary, we want to get a solid footing while we are under 1000 strong, so that we are better prepared for the participation of 5,001 international family historians.
    – GeneJ
    Commented Nov 23, 2012 at 19:36

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