Since numerous pundits have noted that the internet is the biggest “mind” out there, it might seem that Ralph Waldo Emerson shouldn't have limited himself to little ones. Eight years ago, when I posted the 2007 December column I chose for my date tie-in the dissolution of the Soviet Union. That column was posted on December 31 and I noted then that I was “accepting Wikipedia as my authority”. Not that it really matters, but this time I’ve chosen to post on December 26, and once again I'm accepting Wikipedia as my authority (at least as that particular entry reads today). So? Well, not that it really matters, but I suppose that it's fair to ask on which of these dates the Soviet Union was actually dissolved.
The answer probably depends on precisely how you're determining the dissolution. Was it when Gorbachev resigned, or when Yeltsin declared something specific? Maybe when the first (or should it be the last) member states of the Union left for good? I suppose they're all legitimate dates, and that probably means that anywhere from the 26th to the 31st would be the "right" one. In the long run, it doesn't really matter.
It is, however, worth noting that things had a way of being more definite. When we read something in a book it was an established fact. On Wikipedia it's a fluid one, waiting for the next edit.