Translation:It is exactly eight thirty.
"8:30 sharp" is not a full sentence, just a subject. It has no meaning. "hachi jikan han choudo desu" is a full sentence meaning that something IS in fact eight thirty, like the current time, the schedual for a meeting, an item on your birth certificate, whatever. "8:30 sharp" isnt even enough to say the current time is 8:30. It's just a half formed idea.
I agree cuz if you click on the word ちょうど duo says it means 'sharp' as well as 'exactly' so it makes sense. But i think it not because when someone says "what time is it?" You can say "8:30 exactly" or "exactly 8:30" but you cant do that with sharp "sharp 8:30" would sound weird. Even though it saysちょうど means sharp as well as exactly.
When referring to time, sharp means exactly. Seems like it's more often used to refer to the future, as in "The show will start at 8:30 sharp" or "Be there at 8:30 sharp".
When referring to the present time, I'd be more likely to say it's 8:30 exactly (or "on the nose" or "on the dot"). So these time sentences sound awkward to me. Can someone tell me if they sound awkward in Japanese too?
I'm German too and this is a bit weird for us. Most of the world uses polychromic time which can be seen as a more loose understanding of time. When a German says "it will happen at nine" he usually means 9:00 while in most parts of the world when people say that it might happen at 9:15 or 9:30. (This even applies to bus and train plans in some counties). But when they say "sharp" they mean 9:00 exactly.
"With regard to adverbs, kanji don't exist for the most part; (they are) fundamentals one writes in hiragana. [list of examples]"
I think that if you write it in kanji, it's going to look like "the right degree" (as a noun) rather than an adverb, which might confuse other readers, but it's quite possible I've got the wrong end of the stick.
It's also sometimes easier to read when the auxiliary bits are in hiragana, letting the nouns and verbs stand out a bit better.
ちょうど is an adverb. In either case, if ちょうど is removed, it would just say "It is 8 o'clock (right now)". Since it's an adverb, as long as it is next to what you're trying to emphasize, then it is fine. Like in English, it could be read as "It is 8 o'clock EXACTLY" or "It is EXACTLY 8 o'clock" but it still has the same meaning. So it could be in front or behind the time, but it needs to be connected to it.
Unlike 今, it can't have a particle in between ちょうど and the time otherwise it's just grammatically incorrect. Think of it like an adjective, it has to be attached to whatever you're describing.
Google translate is notoriously bad so I wouldn't trust it. There is nothing in the original sentence here that means am or pm. (That would use 午前, or 午後 )
It's possible Translate was converting it from a 24-hour system to a 12-hour one so am was thrown in as clarification
When saying eight o'clock it's like saying it is 08:00 sharp. When then adding the 'thirty minutes sharp' it becomes a bit convoluted what you're trying to say.
This is just how I interpret it and I'm just correcting the english. I do not have enough knowledge in japanese to help you if had problems with that language.