If by "approximate decade" one means "the event occurred either during this decade of during a nearby decade" e.g. it may have been in the 1940s but it could have been the 1920s or 1930s, or 1950s or 1960s --
then I don't think '"1940~/1949~" conveys that. I think that conveys "the event occurs sometime between times A and B where A is approximately 1940 (could have been 1937,...) and B is approximately 1949 (could have been 1950, 51, etc.)
In other words, '"1940~/1949~" would be somewhat more precise (maybe a lot more precise) than, say 194~. But then, it depends on what you are trying to convey. "1940~/1949~" would certainly be appropriate it that's what you mean. And in fact it seems like a more realistic use case to me.
> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of Glen Barnes
> Sent: Friday, January 08, 2016 3:22 PM
> To: [log in to unmask]
> Subject: Re: [DATETIME] Approximate decade precision dates
> Going with "1940~/1949~" would work at a pinch but as you say it isn't
> 'correct' in that you can't determine if the item _covers_ 1940-1949 or was
> made _some time between_ those dates.
> So +1 for allowing ~ and ? on decade and century precision dates.
> On Fri, 8 Jan 2016 13:01:47 -0600, Hannah Tarver <[log in to unmask]>
> >I believe I asked about approximate decades a couple of years ago and,
> >at the time, the closest appropriate fit was an interval with
> >approximate start/end dates, e.g., "1940~/1949~" for "ca. 1940s." We
> >have been using this notation for our items, since dates of varying
> >approximations happen quite frequently with cultural heritage items.
> >However, if it is an option, I would support a specific notation to
> >express an approximate decade to help distinguish between "a particular
> >date in this approximate decade" versus "a range of time with
> >approximate start/end dates."