What's the shortest abbreviation for a full date (day, month, and year) recommended by the Chicago Manual of Style?
I know CMOS recommends against all-numeral dates, so I'd rather not use those. (I know that it says that, when absolutely required, one should follow the ISO standard: "YYYY-MM-DD".)
I've seen it recommend "Mon. D, YYYY" (e.g. "Jan. 1, 2014"), but I'm not sure if that's the shortest date format it recommends. For computer usage, it can still be pretty long.
Best Answer
The Chicago Manual of Style's treatment of abbreviated dates addresses two aspects of the subject: informality and ambiguity. The guideline in the sixteenth edition (2010) that you allude to in your question mentions both of these aspects, but it focuses primarily on ambiguity:
Evidently, Chicago views the all-numerical slash style of date writing as being informal—which may or may not create a problem in tone, depending on how formal the surrounding text is—but the more serious problem from CMOS's perspective is that readers may not be able to tell whether (for example) 4/5/2017 refers to April 5, 2017, or to May 4, 2017.
A subsequent CMOS guideline suggests the ISO format (again) but also other unambiguous short forms:
In this guideline, although the imperative to avoid ambiguity again receives attention, the governing idea seems to shift to formality versus informality. After all, there is nothing ambiguous about the date 5 Oct 2003—and yet CMOS endorses its use only "in documentation and in tables" while insisting that in main text the full date always be spelled out in full. The "therefore" that CMOS inserts before making its formality-based recommendation is, therefore, clearly specious. Nevertheless, it is CMOS's advice, so if you are following that style guide, you had best reconcile yourself to spelling out dates in main text and limiting your use of short forms of the type "5 Oct 2003" to notes, tables, and bibliographical entries.
Finally, CMOS identifies three alternative short forms for the months of the year, as follows:
CMOS offers the following assessment of these three systems:
Once again, opposition to perceived informality (not ambiguity) leads Chicago to oppose using abbreviated months in main text and, indeed, anywhere else not excused from the normal rule owing to "space restrictions" (which in practice usually refers to tables, charts, infographic labels, footnotes, and bibliographies).
To return to your original question, CMOS offers the following style guidelines for handling dates:
It is worth emphasizing that Chicago cites (at 10.40) the periodless "1 Jan 2014" format as the one favored "in computer systems"—so if you are using dates in the context of computers, you might follow CMOS's hint and adopt the "1 Jan 2014" format as more appropriate to your particular context than the "1 Jan. 2014" format would be.