Hyphens, En Dashes, Em Dashes

Q. While The Chicago Manual of Style still supports a no-hyphen version of “up to date” when not before a noun, Merriam-Webster appears to support using hyphens in all cases. I am not sure which to advise my clients to use.

Q. I’m proofreading a book that was previously published in the UK for forthcoming US publication. The hyphenation of “century” compounds using BCE/CE preceding a noun is inconsistent throughout. Examples: “A first-century-CE graffito from a wall in Pompeii”; “A second-century BCE satire.” My inclination, guided by CMOS 7.94 (on multiple hyphens), is to follow the second example, without a hyphen before BCE/CE, which is also how the UK edition was styled. I can’t seem to find any CMOS guidance that specifically addresses this issue, though. Is my inclination sound? Many thanks for any help.

Q. Hi. I have a question regarding the use of the em dash between two independent sentences (as in CMOS 6.91, last example). I understand that the dash can be used in place of a colon when introducing a list; however, when it is used to separate two independent sentences, as a semicolon would be used, it reads as a comma splice (as in your example): “The number of new cases has been declining—last week’s daily average was the lowest since January.” Wouldn’t a semicolon or period be better than an em dash in that example?

Q. Is it acceptable to hyphenate an approximate measurement? Here are some examples: “I boxed up two-hundred-something widgets.” “It will take five-or-so days to complete.” “I need two-and-a-half months for a project of that scope.” (A half month is not a specific number of days.) Thank you for your help!

Q. Merriam-Webster lists “fact-check” as a verb (with a hyphen). But what about when it’s used as a noun—as in, “Oh no, not another fact check!” My guess is that it’s not hyphenated, but I would like to see an entry on this. Thank you.

Q. Should “cotton gin maker” have a hyphen? Does “cotton gin” here serve as an adjective, necessitating the hyphen? I’ve consulted CMOS and am still not quite sure. Thanks!

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?

Q. Do open compounds like “face mask,” “cell phone,” “sea level,” “high school,” and “life science” (all identified as nouns by Merriam-Webster) have to be hyphenated before a noun?

Q. Hi! Is it ever appropriate to follow an em dash with a period if it’s the terminus of the sentence? Thanks!

Q. How would you handle “early-to-mid” + “century”? “Early to mid-twentieth century”? “Early-to-mid twentieth century”? “Early-to-mid-twentieth century”?