In the US, there is no law or regulation. It’s decided company by company. We usually distinguish between vacation days and sick days, and the number of hours for each accumulate throughout the year based on the number of hours worked, with more senior employees having a higher ratio (meaning they accumulate hours faster). The total number of hours are generally capped (eg, they can’t go above 240), but they do carry over year to year. Some companies (and I believe this is required in some states, like California) must pay out the remaining vacation hours when the employee leaves the company, so that if you leave with 120 hours of vacation on the books, you get three weeks vacation pay in addition to any additional severance package. That does not hold for accumulated sick leave. These are both considered “paid time off” (PTO) because employees are paid their salary/hourly pay. When I left my last position, I did so with 240 hours of vacation that they had to pay out, which was in addition to my hiring bonus and moving allowance at my new employer. It came in handy.

Other companies do what’s called “unlimited paid time off.” This means there’s no pre-existing cap and that vacation and sick time get bundled together. It’s all at the manager’s discretion. Depending on the company, though, it can be a disadvantage. Corporate culture can be such that people are discouraged from taking time off, and there’s no vacation pay out if you leave, because you don’t have set hours on the books. Americans in general take long weekend or week-long vacations, sometimes up to two weeks. Depending on the role (and the nature of the vacation), they’ll still work some hours, because that’s often the cultural expectation.

The worst jobs - and this means the majority of service jobs - allow for either zero PTO hours, or will routinely deny employee requests to use them. The above applies to corporate jobs (eg engineers and designers), union jobs, and government work. The person making your pizza or telling you where the shoe department is probably doesn’t get those “benefits,” and if they do, they have to jump through a ridiculous number of hoops (including facing the wrath of their manager) to exercise them.

I’d like the US to have legislation to force minimum levels of PTO, and I’d like to have the culture change so one can say “I’m going to be in Greece for four weeks but will call you when I get back” rather than saying “I have stage three liver cancer and will be getting my organs replaced but I can make the meeting at ten.”