3666 - Three and three sixes

Three and three sixes, total twenty-one
That's the number of this sonnet today
Ten years approaches of this form of fun
Or, if not fun, then duty, some might say
Soon (if I remember) I'll mark the day
On the 5th of September, year 16
I started on that date in '06, way
Back when the world was black and white, or seemed
I didn't like the number three, I themed
A song about that once, but I have come
To accept its existence. It will stay
Despite what I think, hoped, or even dreamed
And so ten years of thought I've nightly spun
Into fourteen lines - it's work and it's play