That odd 'bit' is due to a couple reasons. The first being that I am terrible at remembering dates and anniversaries. Hence, my mental image and timeline of our dating is a biiiiit fuzzy.
The second is that, being two very different types, we have different concepts of when our relationship started.
My coworkers seem vaguely concerned about this. It is commonly thought that women are the ones that care about anniversaries, special holidays and other 'romantic' dates. But really, I don't mind. I much prefer daily kindness and care to a few expensive dates throughout the year.