I translated this as "Time heals everything" and was marked wrong. Is this justified? In English, "all" and "everything" seem to have the same meaning to me. Sorry, but sometimes it is very difficult to translate from the Spanish into English when the literal translation is not how one would say it in English.
Time heals everything is accepted as of December 2018. This is one of those frustrating times that you try to literally translate something only to discover that Duolingo wants an idiom. Remember that "la practica hace el maestro" means "practice makes perfect...."with no teacher to be found anywhere. I've found it useful to take screenshots and have a folder of these to practice and to prevent moments of Spanish Study Rage when I encounter them again. Buena suerte!
You are absolutely correct. However, Duolingo usually wants us to translate literally and we get some rather odd English sentences in the process. It would be helpful if this were on a level marked "idioms" or something like that. Clearly we want to learn the language! But give our beleaguered brains a chance to adjust, you know?
Time cures all should be OK. It is exactly the same as "Time heals all" This section is slighly confusing in that DL asks us to translate Spanish idioms to what would be meant by them in English. The problem is that many of the idioms are actually not so much idioms as proverbs which also exist in English which is why I chose "Time heals all wounds" which DL uses as a translation. But DL seems to be confusing idioms with proverbs which are not the same thing!
A "parabole" is a metaphor from Greek παραβολή (a comparison/ literally- cast alongside). Duo is using an English idiom (Time heals all wounds) to express an equivalent to the Spanish idiom "El tiempo lo cura todo".
Are either (or both) of these sayings absolutely true? You can judge for yourself. Nevertheless, they are commonly heard in both languages.