It doesn't show up in your posts, but just on your own computer, at the top of the forum, but there is also a ticker built into TTOL. To access it, go your "My Home" Scroll down to Main Configuration. Click on EDIT in your Personal Information. Scroll almost to the bottom and you can insert your next trip date. Once you're done, make sure you scroll down to the bottom and hit "submit".
The advantage to you is that you see it whenever you are on the board, but others can't see it, in case you'd rather not have your dates so obvious to others.