Translation:Today is December 5, 2017.
From what I've read, the Chinese language doesn't like to have awkward pauses, which is why a lot of words with combined tones or syllables flow into each other. Like nihao doesn't have the same sound together as they do when they are separate words (ni 3rd tone - hao 3rd tone), because it would introduce an awkward pause.
So to your point, if there's a long pause, it's probably just Duolingo saying it incorrectly lol.
〇 is interchange with 零 here. In traditional Chinese, 零 is far more used. 今天是二零一七年十二月五號。 / 今天是2017年12月5號。
Also, day is usually said as 日 - 十二月五日. But when you counting days, you can only use 日 but not 號. 五日 / 五天 is five days while 五號 is number five or 5th day in a month.
In British English, the day comes first (day, month, year). You have to set up e.g. Excel to recognise either British or US date format. So 5th December 2017 is a perfectly correct answer, it just happens not to be in US English and that does not make it wrong. I have posted to say that my answer should be accepted.
This is marking the answer before I'm halfway done speaking! I didn't pause or anything, but obviously I can't speak as fast as a native speaker. These speaking tests need to allow a few more seconds for us to finish talking. Besides, it's missing the zero audio again. sigh.
English sentences need neither definite nor indefinite articles. Anyway, "it" is a pronoun, not an article. FDR opened with "December 7th, 1941 — a date which will live in infamy" in his famous Pearl Harbor speech. The article in "December the 7th" is optional but in "the 7th of December" is mandatory.