Typically, your employer will provide you with a total number or vacation hours per year. So if your employment contract states that you are eligible to earn 80 hours of vacation time, you will accrue 1.54 hours of vacation time each week you work. This is the total vacation time you are allowed to accrue, divided by the number of weeks in each year.
Vacation leave is accrued on a weekly basis, typically tracked by the number of weeks you work. You are therefore eligible for more paid time off based on the number of full work weeks you have logged since your start date or the last time you took a vacation.
Given a typical nine-to-five job, you would be able to take 10 work days off (or two weeks) at your discretion with the 80 hours vacation accrual example. Depending on the company, the total amount of vacation time may be capped at a certain amount, which, once you have accrued your total vacation time, you are no longer eligible to receive more until you have used your current time.
Additionally, some companies offer increased vacation time to senior employees. For example, you can only accrue 80 hours during your first two years on the job and this gets increased to 120 hours of vacation time at the start of your third year on the job.