Past and Present Perfect in Japanese
I was given a further question (in the coment area of the former post), so I will try to explain how we distinguish between past tense and present perfect.
We don't have present perfect as a tense. We express both past tense and present perfect in the same way.
I ate ham yesterday. kinou hamu wo tabeta (kinou means yesterday)
I've already eaten ham. mou hamu wo tabeta (mou means already)
To make the difference clear, we have some ways to distinguish between them, by adding some words in case of present perfect.
(1) When it means that something has finished, we add '-te shimatta' at the end of the sentence.
mou hamu wo tabete shimatta. (shimatta is the past form of shimau, which originally means 'to finish.')
kare wa itte shimatta He's gone.
In colloquialism, it often changes into '-chatta.'
mou hamu (wo) tabechatta.
kare (wa) itchatta.
(2) When it means that you have experienced something until now, then we add '-ta koto ga aru.' 'koto' means 'a thing' or 'a fact.' '-ga aru' means 'There is' or 'I have.'
I've seen a koala in Australia.
Osutoraria de koara wo mita koto ga aru.
(Literally it would be translated as 'There is a fact that I saw a koala in Australia.')
(3) When it means that a situation has continued from the past until now, we add '-te iru' or '-te kita.'
He has been in hospital for a week.
Kare wa isshuukan nyuuin shite iru (isshuukan 'one week' nyuuin 'to be hospitalized')
Researchers has shown that the global warming will not stop so easily.
..... wo shimeshite kita (shime-su 'to show';si automatically turns into shi in Japanese.)
One confusing thing is that we use '-te iru' for present progression, too.
She is singing (now).
Kanojo wa (ima) utatte iru
She has been singing in the bar (since she was 20).
Kanojo wa (hatachi no toki kara) sono baa de utatte iru
You would probably ask how we tell one from the other. It is not very confusing to us. You can know which is meant, because you can guess whether the speaker says something about the present or about a coninuation of events or actions.
Do you think Japanese is a devil's language? No, Japanese is easy. Even a little child speaks it here in Japan!