Which of these phrases is correct?
1. If none of the dates entered in the previous three fields is within
2. If none of the dates entered in the previous three fields are within
Both are correct:
1. If none of the dates is . . . .
2. If none of the dates are . . . .
It’s uncertain who started the notion that none requires a singular verb, but it’s pervasive, both in the US and Britain, and seems to have been drummed into the heads of generations of schoolchildren. However, all the usage guides—and the usage notes in every dictionary that I can find—are unanimous in saying that it’s wrong.
The argument stems from a misunderstanding of where the word comes from. People assume that none is a condensed form of no one or not one. As both always take a singular verb, the argument goes, so must none. However, the amateur etymologisers have got it slightly but seriously wrong. Our modern form none comes from the Old English nan. Though this is indeed a contraction of ne an, no one, it was inflected in Old English and had different forms in singular and plural, showing that it was commonly used both ways—King Alfred used it in the plural as far back as the year 888.
The big Oxford English Dictionary has a whole section on the plural form of none, pointing out that it is frequently used to mean “no persons” (with writers preferring no one when they mean the singular) and that historical records show that its use in the plural is actually more common than in the singular. There are examples cited in the entry from many of the best English writers (and there’s also an instance in the Authorised Version of the Bible: “None of these things move me”, from Acts, chapter 20). On modern usage, the Merriam-Webster Dictionary of English Usage says, “It appears that writers generally make it singular or plural according to whatever their idea is when they write”.
Such writers, me included, follow the sense—we use the plural or singular form according to whether it’s one or many things that we’re writing about. This grammatical construction, which is based on sense rather than form, has the grand name of notional agreement or notional concord, and is very common (so common that we often don’t notice we’re doing it).
So none of you are right when you accuse me of being ungrammatical.