One thing to note is diary is singular, never "my diaries". Or maybe only if you actually have several physical books of them that you write into, but this is hypothetical - I don't see why anyone would. My journal / my journals works either way, but I'd be inclined to use the singular there as well.

Hi Liusu, Most people feel that they are both the same, but many feel that a journal is more technical and factual with events, times, etc. whereas a diary is more about feelings and personal thoughts...more personal than a journal. I feel that a diary is more about your personal life, and a journal more about your professional experiences. Good question! I hope this helps! Keep learning! Regards David

Either works, however, a diary usually is kept daily, with a shorter amount of writing which is done every day. A diary is also typically for the span of one calendar year. Journals are a little more open-ended, and, as others have mentioned, could cover a wide array of topics.

Both are acceptable. As the other answer indicates : a journal could be for lots of things. It could be a professional journal or a newspaper or whatever. Usually the word diary indicates a much more personal, private thing.

You can use either. Diary may be more specific, but both are used.