steve dave has only worked one place so of course he's only heard of it one way. I have worked many places and have always heard it measured in weeks (1 week = 5 days) when like looking at bullet points as a job offer. Like, 2 weeks vacation or 1 week vacation in year 1, 2 weeks year 2, 3 weeks year 5 or something. Increases generally go up in 1week/5 day/40 hour increments.
And then it's usually translated into a rate where you get 1/26 of 2 weeks or whatever added to your PTO balance every paycheck. That's how it's been at most functioning organizations I've worked for.
Granted I've only worked at one place for the last four years where it's been unlimited. Recently they asked us to put the vacation requests into ADP! Even though it's unlimited! (really it's probably good because more people take not enough rather than too much)