"How is the evening Juma?"
Translation:Habari za jioni Juma?
In this case, I believe the use of ya or za with Habari depends on the country. But, I should have been more clear in my explanation. My apologies.
Ya /za should agree with the preceding noun in this case habari (news). Habari is an N class noun. Therefore, za should be used grammatically speaking since ya is for singular N class nouns and za is for plurals.
However, in Kenya, this rule is not followed. In Kenya, they say habari ya jioni, mchana, asubuhi, etc. I am told that in Tanzania the grammatically correct za is used. But, if you use za in Kenya they will understand what you mean. You will just sound like a tourist, which is fine.
Some people explain that za is used for general politeness and ya is used when you really want to know what's going on. See website below. http://www.learnswahili.net/swahilicourse/learnswahilicourse_lesson2.html
And, perhaps this is why even Duolingo uses ya and za at different times. What is the news of the day? (General) vs. What's your news of the day. (Personal)
So maybe Kenyans choose to be less formal and that's why it is commonly used in Kenya. I don't know. I just know Kenyans say Ya even though it should be za if you are following the rule.
One disclaimer: It could also depend on where in Kenya. I stayed primarily in Nairobi where most of my friends live or work.
Soooo....1) Habari - noun cl. N-N 9/10 without plural form. Means - news, information. If we think about - what are the news - should be -pl.form " za", but both forms should be accepted. 2) The difference between " jioni" and "usiku" is...as between evening and night. :)