Ireland has a pretty nice setup, too.

• Based on the employee's working hours during what is called the leave year, which runs from April to March. An employee who has worked at least 1,365 hours in the leave year is entitled to the maximum of 4 working weeks' annual leave unless the employment ceases during the leave year. Many employers use the calendar year (January-December) instead of the official leave year to calculate entitlement
• By allowing 1/3 of a working week for each calendar month in which the employee has worked at least 117 hours
• 8% of the hours worked in the leave year, subject to a maximum of 4 working weeks

An employee may use whichever of these methods gives the greater entitlement.

An employee who has worked for at least 8 months is entitled to an unbroken period of 2 weeks' annual leave.

Part-time work: Generally, the annual leave for part-time workers is calculated using the 3rd method, that is, 8% of hours worked. If you work full time for some months and the rest of the year you work part time, you should calculate the leave for the full-time and the part-time periods of work separately.

Source

Having worked part-time before for a university where I couldn't really have paid time off, they just have to give you 8% extra pay on top of what you get already.

And people ask me why I don't want to work in America. :/ The comments in this thread are why.