Last year, I made a "perpetual journal." Every day of the year has its own index card. For the first year, it's basically a regular journal. (Except instead of an attractive notebook, you have an unwieldy stack of notecards). But after the first year, it's M-A-G-I-C. At the end of the day, you don't just write your journal entry - you also read the entries for prior years. It's fun to see how similar and dissimilar the entries can be.
For example, my entry for July 23, 2011 is: "We got married!!! And had a WONDERFUL wedding!" My entry for July 23, 2012 will obviously be a little different (as fun as our wedding was, we're not about to make it an annual tradition).
I followed this excellent tutorial on Design*Sponge to make my journal. My journal is not very pretty, but it gets the job done:
Someday I'll get a proper box for my journal; and if I'm feeling super ambitious, I'll make dividers for each month. But for now, the point is just taking a moment every night to jot down one or two highlights from the day.
Confession: sometimes, I slack with my perpetual journal. Four or five days pass and I realize, "Crap! My journal!" But I managed to write an entry for every day in 2011. And I'm so glad I did because I love flipping through the index cards and glancing at random entries.
For example, here's a fun memory that I had completely forgotten from January 4, 2011: "I heard Bob Newhart's piece on XM about baseball, and then played it for Nathan on YouTube." There's no way I would recall a detail like this on my own.
Poor February 29th! It's still waiting for an entry. Don't worry, February 29: 2012 is your date with destiny. (And then we'll see you again in 2016).
I love my perpetual journal and if you have ever flirted with the idea of keeping a diary, I highly recommend this method. You can make it while watching a movie, and then it only takes seconds to scrawl an entry at the end of the day.
p.s. You can even make the calendar as you go. Who says you have to stamp all the dates in advance? And who says you even have to stamp the dates at all? The perpetual calendar will work just as well if you just handwrite the date yourself.