"What time is it now?"
It is normally written without the comma, but a comma could be added without problem. Commas, in Japanese, do not serve as strict of a grammatical function as they do in English. They usually just serve to indicate a slight pause in the dialogue.
As particles such as は are often omitted in casual language, often the omission would create a 'gap' in the flow of the sentence.
For now, and specifically in this set phrase, I would simply remember 今何時ですか as the default way of saying it.
I've been using a Japanese keyboard instead of the word bank because I find I learn better when I have to find the characters for myself. And I put in "今は何時です" without the か at the end and got it right. So it seems there's some things Duolingo is more relaxed on, but still seems weird
If you are asking why it can't be 時何 instead of 何時, it is natural in Japanese that the principal question word (character) 'what' be placed first in these compounds.
何人（なんにん）How many people?
何度（なんど）How many times? / Which time? / What temperature?
何個（なんこ）How many pieces?
If you're asking for an etymological explanation as to why that is, I am not knowledgeable about that and the question seems superfluous for a basic Japanese program discussion.
何時 is the correct kanji for いつ (in addition to being the correct kanji for なんじ）. Writing いつ in kanji is somewhat irregular and can be confusing for Japanese as well, so it is almost always represented in hiragana. Duolingo is correct on the reading, just not reading it correctly given context ;)-
If you come across it again I would suggest reporting it.
In informal Japanese, a rising intonation at the end of the final word can indicate a question without the need for か. Informal Japanese, however, wouldn't normally use です and would omit the は particle, so you should be using か in this sentence.
I have a feeling that they may have created a rule that allows question sentences without か, as it is allowable on occasion under certain circumstances.
You shouldn't. Casually, it is often shortened to 「今何時？」.
As Japanese is actually spoken, 今 is included by default when referencing the current time.
The sentence "何時ですか" makes sense because it means "What time is it ?". When you ask that question, it is often implied that you ask about the current time, so the "now" isn't really needed. However this exercise emphasized the "now" and therefore it suggested that you had to add "今" (now).
Your first sentence begs the question. Because it makes sense to you doesn't mean it is used that way or even that it does make sense.
I would appeal to my years living in the country and communicating exclusively in Japanese (aside from short English lessons), but more convincing evidence can be found by simply searching the internet or textbooks.
As I don't like to make unsupported assertions, I just asked this question on HiNative. It's in Japanese, but it confirms that it is not only better to add 今, but will alleviate potential confusion. https://hinative.com/en-US/questions/11791997
Wouldn't the meaning of 何時ですか in depend on the topic that we are talking about? If we are talking about lunch and you ask this, wouldn't people assume you were asking at what time (hour) we were going to have lunch? In some sense 何時ですか literally does translate to "What time is it?". In the English sentence however, the meaning of it automatically references to right now. This is just like you said. In Japanese however, the imaginary it in this sentence references what we were talking about, which in this case was lunch.
By including 今, we specifically want to know what time it is now. Again, like you said, this isn't needed in English where the it automatically states this.
On the other hand, if I out of nowhere would ask someone: 何時ですか, wouldn't they assume that I meant right now?
You seem to have a lot of experience so I this is more of a question to you.
For the most part your understanding is spot-on. When the context is already clear the 'it' can be omitted.
About the last part though, someone might assume that you mean the time 'right now', but they will also likely feel that you could have phrased the question more clearly/specifically.
Today is Friday 31st August 2018 - still finding errors in the Japanese course - 152 days now (Yes, I know ...it's a beta course...)
Both なん and なに are kun'yomi readings for 何. 何, when combined to form a compound, is subject to the determined pronunciation of said compound. One compound might have an on'yomi reading as well as a kun'yomi reading, but they are each subject to their own determined pronunciation rule.
It is not rendaku. Rendaku is generally an inflection on a non-primary mora that is not necessarily part of any normal reading.
Take 時々（ときどき）and 花火（はなび）, for example. Neither どき nor び are included in on'yomi or kun'yomi readings.
Technically, in highly casual spoken Japanese, if you put enough rising intonation at the end of the sentence (without か) it will sound like a question, thereby becoming acceptable as a question.
In written Japanese and standard spoken Japanese you should not omit the か.
DuoLingo, IMO, shouldn't accept it without the か.
You forgot the は particle. は signifies the topic of the sentence. I found this website to be extremely helpful in this topic. Also, it helps to convert the じ into 時 if talking about time.
何人（なにじん）ですか？ proves you wrong. Even though the same sound follows 何 and です does as well, there is no correlation.
By the way, there are two possible readings for 何人: なにじん（Type of person; breed of human); or なんにん (how many people).
Whether the い gets dropped or not largely depends on frequency of use and how it sounds to a natives ears. You just have to learn as you go.
i am sorry, but i do not understand why you bring the kanji 人 in this discussion. It is not used in this frase. However you are correct it can be read as hito if it stands alone, as nin if before a nummer or nummerical, or as jin before for example a country to denote that person lives there or has lived there. As for the discussion on the kanji 何, i have asked my japanese teacher and she told me that if used before です, the い is silent just like the u sound is with desu. But it is possible that i understood her incorrectly i am still in my first year after all.
Historically, the currently 'silent k' was pronounced, and over time became omitted by more and more people and gradually fell silent.
To be clear, I didn't mean say that 'desu' is the same as 'knife'. I said that asking the question about why they are voiced/devoiced is the same. .. On second thought, I should have said 'roughly equivalent' (In 100 years they may be fully equivalent).
Not correct. Japanese is not English. After being in an exclusively Japanese-speaking environment for a decade, I can assure you that if you conflate 何時ですか with 今(は)何時ですか you would be wrong.
The word 'it' is by its very nature context-reliant. In English and some other languages, the 'it' part of 'What time is it?' has been tacitly accepted as meaning 'the current time' (barring other context). The 'now' is implied, but not directly stated.
In Japanese, however, there is no such tacit understanding. The response to 'What time is it?' (何時ですか) without clear context would be the equivalent of 'What time is what?'.
While some people might make the assumption that you are talking about the current time, that does not make the sentence correct in itself.
There is a reason that all of the Japanese language texts and online resources (including this one) include the context (今). Dismissing this would be reckless. Telling others to dismiss it would be disingenuous.
I would say that it is an oversight in the course if it doesn't suggest that you use 今.
I understand the reluctance of many who don't understand the need to incorporate the 'now' aspect to the question and consider it should be obvious. That is because 'now' has become implied in English when lacking a specified time indicator. In Japanese, it is not naturally implied.
Look pretty much anywhere for language instruction and they will tell you that the way to ask the time is 今（は）何時ですか？Until Japanese language changes to assume that a time inquiry without specification implies the present this will remain the de facto way to ask the question.