As someone else noted many of these ideas won't work in countries where large chunks of payed holidays are enshrined in law.
In Australia most of us have 40 days per year that roll into the next year if you don't take them. There are options for employees to turn in some of their days for cash if they accrue a lot which is nice.
Err.. most of us have 4 working weeks of paid vacation per year. That's 20 days, not 40 (although it excludes paid sick leave - usually 10 days - and public holidays). Vacation leave usually rolls over, but sick leave varies. Public holidays don't.
(I'm Australian, and I've never seen variance on this except on the roll-over rules. The one exception is my current employer that offers an extra day off on your birthday)
In Australia most of us have 40 days per year that roll into the next year if you don't take them. There are options for employees to turn in some of their days for cash if they accrue a lot which is nice.