Duolingo doesn't believe in theory, they only believe in us getting things wrong until we get them right.
DL's philosophy is that its users should learn the same way that children do.
I was wondering why there was not a theory section and not really sure what I would be learning in this section. Good reference article regarding present perfect tense here http://www.studyspanish.com/lessons/presperfect.htm
Was helpful to me!
Is it not possible to write 'he didn't eat today' ? I'm not sure that the difference between 'he didn't eat today' and 'he has not eaten today' exists in spanish.
You use the perfect present tense when the action is done and over with, but you have done it within the day you are still at, otherwise you would use preterite "yo comi" with an accent on the "i"
From whatever English I have learnt , I know that when one specifies the time of an occurrence one uses "past perfect" ie in this case "He did not eat today"would be in order. If the time is not specified then one says ""He has not eaten"
- He has eaten - present perfect - the action is done but affects the present
- He ate - simple past - the action was at some point in the past
- He had eaten - past perfect - the action happened before some event in the past.
If it the subject is "it" then can you leave that out but if the subject is "he" or "she" then you have to leave it in for clarification?