6 years is 2190 or 2191 with 1 leap year or 2192 with 2 leap years.
As of writing I created my account 2170 days ago. It is by far my most visited site (at least once a day). Sure the content isn't as great as it use to be, but I expect that with the increase in traffic and submissions. It is still head and shoulders above the rest though.
Happy birthday HN!