That's an interesting format, and I have to emphasize that admissions offices LOVE creativity. Moreover, it will stand out from the rest, and whoever reads it will remember it, which will help you when they determine whether to admit you. I have two caveats, however:
1) How long is it? If it's more than 2 pages, you have to shorten it. Thus, your format may not work out as well if you've got multiple diary entries. If you focus on one or two diary entries, then that might work.
2) How casual is the writing style. You don't want to sound too casual, colloquial, or slangy. It may be a diary entry, but it should maintain a certain level of formality.
E-mail it to me if you want me to take a look.