i finish today (since it is today there can be no "by" since that has passed)
Sounds strange to me, but apparently it is being used occasionally. Google "I will finish today" 816'000 05/05/2013 (okay) "I will finish by today" 19,800 05/05/2013 (sounds strange when isolated) 'I finish by today" 9,370 (sounds stranger when isolated)
Well, I use Duolingo to learn Italian AND English at the same time, since I'm not native xDD I like to think that by the time I'm finished with Italian, I'll become even better in English <3
You are not a native English speaker? Wow! I could not discern that from your posts.
This seems to be another instance of Italian using simple present to express a near-future event. "I will finish by today" is a likely English idiom paralleling the gist of the Italian.
In English we "cheat" on the future tense by use of present continuous:
"What will you do this afternoon?"
"I am going to the store" or "I will be going to the store" mean the same thing.
In Italian, there sentences like: Arrivano stasera - literally, "they arrive this evening" in idiomatic English would be "They will arrive this evening."
So, it's just idiom.
You cannot possibly say "I finish by today" in English. It is a total nonsense.
What could be the difference between "fra" and "entro"? Which one would be used together with "domani" to say "by tomorrow"?
Entro, I think.
"fra" = "between" or "in" (the latter as in "in two days")
"entro" = "within" (as in "by" or "no later than")