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For use in mathematical articles, Wikipedia recommends using the unicode minus (the − entity). While we usually defer to Wikipedia on matters of style where no wiki-specific guidelines are in place, I must convey a preference for the regular hyphen character (the one next to the zero key on a UK keyboard).
No keyboards (that I know of) come with a unicode minus button on them, which makes it hard to type. For newcomers, trying to explain the difference between a regular hyphen, a minus symbol, an en dash and an em dash will be extremely difficult, and it will need to be explained each and every time. Although not strictly correct, the use of a regular hyphen will make it easier to type the year numbers and also easier to maintain the wiki, and I think ease of use has to win out on this one.
Do feel free to have your say below (using the {{Forum post}} template) and we can aim to put together a proposal so we can all agree on the best method of covering this.