A colleague has encountered a sentence of the type “This will happen in one-to-two months.” She’s wondering about those hyphens.
And well she should be. They have to go. It’s not optional. Otherwise it’s presenting a type of month with the quality of “one-to-two” in the same way as “two-by-four boards” are boards with the quality of being two inches by four inches. A “moderate-to-severe infection” is “an infection that is moderate to severe”; “one to two months” is not “months that are one to two”.
In cases like this, some people are confused by the use of hyphens in something like “a two-month decline”. But this is not that. In a case like that, the head noun is “decline”, and “two-month” is hyphenated because it is part of a compound modifier. In the case of “one to two months”, “months” is the head noun and the numbers are quantifying it – they are not adjectives, they are quantifiers. That’s another point of confusion some people get into: treating numbers as though they were adjectives. (It doesn’t help that CP Style, presumably for reasons of readability in newspaper columns, prescribes, for instance, “two-million” rather than the standard “two million”.)
“One to two months” is not a set of months with the quality “one to two”; it is “one month to two months” with the first “month” removed. (A similar deletion, but of the final “months”, is seen in “a month or two”, which we don’t write “a- month -or-two”.) We can use a dash to replace “to” in, for instance, “1–2”, but we don’t use dashes (or hyphens) and “to” with number ranges.