You can run `sysctl kern.boottime` to get when it was booted and do the math from there.

I also can't reproduce. I want to say I have encountered this issue at least once, yesterday I before rebooted my uptime was 60 days.

But it's not instant, it just never releases connections. So you can have uptime of 3 years and not run out of connections or run out shortly after hitting that issue.