Translation:It is not three o'clock.
ありません is the polite/formal version of ない. じゃ is the casual, spoken version of では.
So, all in all, じゃない is a considerably more casual version of ではありません
One can also say ではない and じゃありません, and they fit somewhere in between, though I'm not versed enough to comment on where exactly each one lies or how big the gap is.
@Andrew-Lin yeah, that makes sense to me, but I'm not a native speaker, so I'm not sure if that's how it actually goes.
Also, I asked my (native Japanese-speaking) partner about じゃないです and it took her a while to register what I was asking because she doesn't think there's anything wrong with じゃないです. Even after I explained that じゃない is a negative verb form of です, and by adding です on the end like that "for politeness" is essentially treating it as an い-adjective, she told me that Japanese people don't really think that deeply about it f(^_^;
If you really want to break it down... the "de" indicates a state of being, while "arimasen" means "there is not." So, literally, it means, "There is no being 3:00," or in other words, "It isn't 3:00." If we just said, "Sanji wa arimasen," that would mean something like, "There is no 3:00."
"De wa arimasen," "Jya arimasen," and "Jya nai" are all forms of the same construct, which means "it isn't."
PM in Japanese is 総理大臣... just kidding, that means "Prime Minister".
The one you're looking for is "p.m." and in Japanese, it's 午後 (ごご). So, if you see/hear these characters in the sentence, you'll know you should include "p.m." in your answer.
Side-note: the convention in Japanese is the opposite of English. 3 p.m. = 午後三時
Well, "Living in quiet retirement, dividing one's time between yard work and intellectual pursuits" is such a long way to say 晴耕雨読, but that's what it means. When learning a new language, you should discard any preconceptions about what it should be, and embrace what it is.
Why is the "は" pronounced like "wa" instead of "ha?" I thought it only did that when it was being used as a subject marker, but in this example it's being used in a verb. Could anyone please explain if this is just an irregularity or if は is also commonly used to make the "wa" sound?
Well, です itself is considered an irregular verb, so this pronunciation of は as wa is irregular too, in a sense. That said, the は in ではありません is, etymologically speaking, behaving as a particle, so it still complies with the general rule of thumb.
However, は is used as the topic marker, not the subject marker, though the subject is commonly also the topic.
三時 in this sentence is actually the object, not the subject. The subject/topic is implied by the context, so the は particle is also dropped. If you wanted to include a subject, you could say something like 「今は三時ではありません ="(The time) now is not 3 o'clock", and it falls into the same pattern as です (AはBです = "A is B").
"Now" doesn't appear anywhere in the Japanese sentence.
You could infer from context that the speaker most likely meant "now", but we don't have any contextual information for these exercises, and something else (e.g. the start or end time of a meeting) is just as likely as to not be 3:00. So it's not valid to assume "now".