[cuonglhvt]

Another answer:

I think Japan just wanted to be more in line with the West, so they adopted the same calendar. No big deal.
As for kanji, it's almost impossible to use straight romaji (the alphabet) for writing Japanese because there are so many homonyms. Even just writing in kana points out the same thing, that kanji is necessary to distinguish word from word.
If you can understand Japanese, then just try it. Write a bunch of sentences out in romaji and see how easy/difficult it is to read it. Not only does it become confusing, but it takes up more space. In the space that you could normally write one kanji, you might have to write 5 letters.
And why would you give up such a beautiful writing system anyway, as if the impracticalities of doing so are not enough?

I saw that the dificulty Japan have to use Romaji is the same difficulty Vietnam have. When I writhe "lý", nobody know thatI refer to 里, 理 or 李 etc... (RI in Japanese). But as I said. When I say, the context makes us understand, so it will be similar when I write. And Vietnamese Latin at the begining was not similar to it is now. They have to improve. I think Japanese Romaji will be similar if it is used widely. (I don't mean Japanese should learn Vietnamese).

And also, why are you talking about things that happened so long ago?

The only thing I want here is to learn Japanese History and compare with Vietnamese. And the only thing to find out the truth is argument.
So don't assume that "what I say is what I think"! Don't think that I hate Japanese!
Don't you find it interesting in studying history of your country? I do!