"Today is Sunday."
星期日 is also Sunday. Report it
I appreciate that Duolingo is at least expanding itself to accepting time travel reports on December 22 when it's only November 22. Screw learning this language, teach me your time-bending ways, Dennis!! Har har. Just playing. I'm sure you meant November.
Both are correct, I think. The use of 是 just makes the sentence more "complete", but it's not necessary, especially when speaking.
These characters for Sunday were not introduced, How do they sound! How many different combinations are there for Sunday!!
星期天 is more common in Mandarin, 星期日 is more common in Cantongnese, 周日 is more common in writing
I found a site to help but it still bothered my that they threw that word in without previously teaching it. https://blog.speechling.com/5-different-techniques-to-indicate-time-and-tense-in-chinese-speech-and-writing/
Totally confused why the answer without (shi) is accepted but it's not likewise in questions form