The End of a Decade, with a Fair Starting Day

I'll let you know when my decade ends.

To do that, I'll first need to figure out when it started. ;)

Now, which starting point will allow me to maximize or minimize something interesting...

Oh, never mind; let's do this with a random-number generator: I get 2017.55793, which rounding to the nearest day (I'll round up), gives me a start to my decade of the 204th day of 2017.

My decade apparently started on 23 July 2017, so talk to me in 2027 about the end of my decade.

P.S. Happy New Year! (Well, in a few hours.)