Yet again, I need opinions from non-US native speakers of English.

I tend to agree to this observation. For example, I believe (but I don’t know of any data that can comfirm it) that the British will say “Half past seven” more than Americans will (I think they’ll tend to say “seven-thirty.”)

I’m curious: Do your textbooks tell you that after the half-hour, one can say “eighteen to four” in two other ways? (“Eighteen of four,” and “eighteen before four.”) And also, which particular textbooks are you referring to?

Speaking of AFfect (as opposed to efFECT), I totally agree with you here, and there’s a great article about this (-Ochs, E. & Schieffelin B. [1989]. Language Has a Heart). Sorry, I don’t remember what text it’s in.

Anyway, the point of “Language Has a Heart” is that affect is built into the grammar of all languages (syntax, morphology, etc.) For example, you can say:

a) He always comments on my appearance. [neutral or positive]
or
b) He’s always commenting on my appearance. [negative, it bothers me]

By shifting the aspect (from simple to progressive), you convey a mood.

Or, In Spanish, you can refer to:

a) mi carro (my automobile)
or
b) mi carrucho (my junker)

With morphology, you can express how you feel about your car–your mood.

But I don’t think time expressions are used to do this. I don’t think the difference between:

a. three forty-two
and
b. eighteen to four

is about mood. I think it’s just more a question about ideolect.

Could it be that your textbooks are drawing upon British English, and you find this different in tendencies you see in American media?

Well, obviously they are. That is the entire point. My books are written in British English, and sometimes I have to double check with the Dopers to make sure they aren’t making mistakes (which definitely happens from time to time) if the construction doesn’t look familiar. As a fairly-well read person, I’m always suspicious of unfamiliar constructions, since I like to think I know the difference between a mistake and a Britishism, but I’ve learned that sometimes I don’t.

Brit here. If I needed to be precise, I’d say, “Three forty-two”, else I’d just round it.

Sorry. Somehow I missed your second post.

From the OP it seemed like you were asking just anyone who spoke English, not specifically native British speakers. Anyway, I don’t think it’s a British/American thing. Like others have said, I think it’s when things are on the 5-minute mark, some say, and you look at an analog clock, it’s easy to recognize that. But when it’s 3:42, ect., people probably are reluctant to subtract 42 from 60 in order to say, “Eighteen of four.”

Well, British English is supposed to be what I’m teaching them (which is never really going to happen, I am not going to speak with a fake accent), but I’d be interested to see what Australian and Irish and Canadian, etc. Dopers have to say about it too.

Basically, I don’t want my kids to ever think “Why did Kyla teach me [useless phrase] when I was eleven?” when they go out into the world and try to use the English I am teaching them. So I try to gather a collection opinion. (Sometimes I am even able to convince my counterpart that it’s equally correct to use one phrase as another; Bulgarian doesn’t have nearly as much variation as English does and she uses Textbook English.) Also, it’s interesting to see what all the different responses are.

A little late but another Aussie checking in.
I’d say twenty seven past five and eighteen to four probably 90% of the time.

I’m British

a. five twenty-seven
a. three forty-two

Your examples are slightly stilted, as you are using very precise numbers

Twenty to four or three forty would be interchangable

Twentyfive to four would make me think foreigner
Quarter to four, ten to four would be Ok, but five to four would be strange

Half past three and three thirty both sound right.

It is something to do with the precision and the number of syllables, and there might be an element of an approaching deadline - say you have a meeting at 4:00 and the time is quarter to four. Under deadline circumstances a deliberate oddness is possible, but that is for emphasis - and is slipping into ‘teutonic’ mode.

Whoever wrote those books may have British nationality, but they would have a hard time passing as British. Generally we don’t know our own rules, but if something sounds wrong it really grates.

For safety I would teach them that it is always minutes past the hour, but you can use alternatives.

Just to muddy the waters, I might say ‘see you at half one’ to mean 1:30, but it would be slightly slangy and informal. We were highly amused that Halb Eins means 12:30.