vacation bank
n. An employee's yearly allotment of vacation days.
Examples
2008
Canadians looking forward to a July long weekend can be forgiven for feeling a little short changed this Canada Day.

With the country's biggest party falling on a Tuesday, failing to trigger three days off work in a row, the public service and many private companies expect staffers to be at work bright-eyed and bushy-tailed both Monday and Wednesday.

In short, if you're not dipping into your vacation bank to make it a four-day break chances are your bosses want to see some output Monday.
—Tobi Cohen, “No long weekend this Canada Day,” The Canadian Press, June 26, 2008
2008
The survey also found U.S. employees tend to divide their time off into one full "power week," utilizing the rest of their vacation bank as days sprinkled across the calendar to make long weekends or extend holiday breaks.

As in 2007, the average U.S. worker has 14 vacation days this year. Just across the Canadian border, our counterparts get an average of 17 vacation days annually.

But if you want a real "vacation envy" complex, consider the vacation banks of European workers. France tops the list with an average of 37 days, followed by Italy (33 days), Spain (31), the Netherlands and Austria (28), Germany (27) and Great Britain (26).
—Sharon Linstedt, “Don't forget to use your vacation time to recharge,” Buffalo News, June 16, 2008
1990 (earliest)
Another feature of the settlement includes a newly devised ''vacation bank,'' which will give Delta pilots much more flexibility in arranging time off.
—“Proposed Delta Union Contract Will Make Pilots Top Paid in U. S.,” Aviation Week & Space Technology, August 13, 1990
Notes
"Workers accrue time pro rata by law," says Kenneth Sulzer, an attorney at Seyfarth Shaw in Los Angeles. "People end up with substantial banks of vacation pay. When they leave, they are entitled to all unused vacation at their current pay rate. Some of our clients are making people take time off as a way of reducing this big collective vacation bank."
—Marilyn Gardner, “Take a vacation. Really.,” Christian Science Monitor, June 30, 2008