On top of that nzuri refers to a thing, when referring to a person, the proper term is "mzuri" which comes from what is know as ngeli or classification of Nouns in Swahili. Since the plural of a person(Swahili: mtu) is watu(i.e. people), the term "zuri" becomes mzuri for a person, and wazuri for people.
Also - I see people using nzuri - I have known the word "mzuri" (good) --- Is that difference in dilect? -- Why not "Juma ni Mzuri" (juma is good) or "Juma ni vizuri" (juma is well) ALSO pao means 'calm' does it not? Finally, would it not be better to say - "Juma iko vizuri'
Look at my earlier response there talking about classification of nouns in Swahili. 'Juma ni mzuri' is correct because a person belongs to the m-wa noun classification family. "Juma ni vizuri" is wrong because 'vi' is for the "ki-vi" noun classification family and then finally 'Juma Niko vizuri' is wrong because that's rude, Juman is NOT a thing but a person, so you'd say: "Juma yuko/yupo vizuri"
Your reply is not very clear. I don't know how noun classes work in Swahili, but in Latin or German, you would need to know the specific noun class of the word "Juma/juma", not of word "mtu", and the word sticks to the noun class. Do all proper nouns indicating persons automatically fall under class 1? Does "juma" change noun class, according to whether it means "week"/"day", or a person's name or a supermarket named in honour of somebody?
It is helpful to explain why "the week is cool" doesn't work here, given that we don't know if it a proper or a common noun, given the beginning-of-sentence capitalization. Maybe because "juma" would be formal/traditional, and the feel of this sentence is informal?
Secondly, dictionaries usually give "week" not "day" as the translation of "juma". Both make sense to me and can be retraced to Semitic roots, but it would be useful to know what is usually meant by "juma", and whether the germanic "wiki" has generally replaced it to say "week", while "siku" (Bantu?) is the usual way of saying "day".