The Supreme Court will consider whether the Second Amendment should apply to the states, and thus whether to overrule United States v. Cruikshank, 92 U.S. 542 (1876). Or is it United States v. Cruikshank, 92 U.S. 542 (1875)? Both citations are commonly used; HeinOnline reports that the 1875 date is given in roughly 60% of law review citations, and the 1876 in roughly 40%. Which is it?
Well, if you want to give the date of decision — which is the modern Bluebook requirement — you should say 1876, since the case was decided Mar. 27, 1876. The reason that many people say 1875 is that, to quote the Supreme Court’s Web page on the subject,
The dates of decisions do not appear beneath the case name in the first 107 volumes of the U.S. Reports. Beginning in 1854 (58 U.S.) the Lawyers’ Edition of the Supreme Court Reports includes the date, though there are some errors and omissions….
Some dates do appear in the U.S. Reports, either in the margin or in the body of the opinion. One edition of a particular volume may have dates while another edition does not. These dates sometimes differ from the dates found in the [Engrossed Minutes of the Supreme Court].
Fortunately the page I just linked to contains the official publication dates, so if you want to include the year of decision, you may do so. And for Cruikshank, the year is 1876.
(Note that the characterization of the issue in McDonald as being whether to overrule Cruikshank is something of an oversimplification, but let’s go with it for now.)