As is often the case in English, preposition use is very flexible - as of today, from today, as from today, from today on, from today onward [s] are all equivalent for the "starting today" sense (but not all of them can be used to mean "up until today"). Any "nuance of difference" is more likely to be related to change over time, geographical regions, and a speaker / writer's sociolinguistic ...
Which is correct: "as of today" or "from today" in the context of ...
" Are you working today? " is a specific question about this day - not this day of the week, but this exact day. For example, it might be a Wednesday, and you know the other person normally works Wednesdays, but perhaps you are enquiring if they took a vacation day. " Do you work today " sounds a little unclear but it could be okay in context. " Do you work... " rather than " are you working ...
You missed out from today onward (without the final 's'), which has become the more common form in American English today. But this is essentially a matter of opinion - syntactically / idiomatically they're all perfectly acceptable.
"From today (on / onwards) Or "As of today" Or "Starting today"
For example: Today (it?) is my brother's birthday. tomorrow (it?) will be my brother's birthday. yesterday (it) was my brother's birthday. In my native languages this pronoun is omitted in parallel sentences, and that's why I'm asking it.
sentence construction - "Today is" or "today it is"? - English ...