I just finished celebrating my three year Iloveyouiversary with my wife. It was three years ago today when I first told my wife that I loved her. My wife thought it was soooo sweet that I remembered this. Here's the thing though. I didn't remember.
This is what I did and what I do for any special or unique occasion I have with my wife. Whenever something significant or special happens with me and my wife, I open up my Google calendar and go back to the day and time that the event happened. For the event I will write what happened (our first date, first kiss, first time we talked, etc) and the day it happened on.
In the description I write details that I am likely to forget but might be useful to remember (like where we ate, how much it cost, impressions I had, etc).
Important thing #1 - I set the calendar event as reaccuring on a yearly basis.
Important thing #2 - I set an email reminder for two days before the event. I find that two days usually gives me enough time to prepare to have a mini little celebration if I need to.
This has ended up working great for many things. I have been able to celebrate our firsttimetalkingiversary, our firstdateiversary, our firstkissiversary, our firstvacationiversary, and of course, our anniversary.
Pro tip: Keep a good journal. I had no idea I would marry my wife when we went on our first date, but luckily I had a good enough journal so that when I did marry her, I could see the time and date of our first date.