Hyphens, En Dashes, Em Dashes

Q. I’ve been looking for a format on writing date ranges but cannot find any. How do I write a range without a death year or without a birth year? Should it be First I. Last (1804–?) or First I. Last (b. 1804)? Or is there any other way? What if you are unsure of the year because sources say different things?

A. If the person in question is no longer living, either form that you show is acceptable if all you know is a birth date: (1804–?) or (b. 1804). If the person is still living, you have the same two options (but without the question mark, and note the lack of a space between the en dash and closing parenthesis): (1984–) or (b. 1984).

If a death date but not a birth date is known, substitute a question mark for the birth date or use the abbreviation “d.”: (?–1890) or (d. 1890). To signal that a specific year of birth or death is likely but not definite, put a question mark after the year: (1804?–1890?). If the dates are contested, additional information may be provided in the text or in a note.

See also CMOS 6.68 and 6.79.