For example, create an entry that is backdated to your birthday or some other day that is important to you (for instance 1/1/1970) and add your contact information, or your itinerary, or whatever the hell you want to to that entry, then mark it as friends-only. Keep that entry updated.
(If you don't trust everyone on your friends list, you can make a custom list.)
You can also do something similar if you forward-date the entry to something like sometime in 2010. This entry will show up as the very first entry in your journal, and it should kind of "float" there until sometime in 2010. However, this seeems better for something like a "FRIENDS ONLY" banner or somesuch.
Mock your inner child.