Or sliding vacations, free time, etc.

/ movable holiday / moveable feast / “bank holiday”

Not a direct translation, but something to work with.

In the UK:
“Under the Banking and Financial Dealings Act 1971, bank holidays are proclaimed each year by the legal device of a royal proclamation. Royal proclamation is also used to move bank holidays that would otherwise fall on a weekend. In this way, public holidays are not 'lost' in years when they coincide with weekends. These deferred bank holiday days are termed a 'bank holiday in lieu' of the typical anniversary date. In the legislation they are known as 'substitute days'. The movement of the St Andrew's Day Scottish holiday to the nearest Monday when 30 November is a weekend day is statutory and does not require a proclamation.”

“The number of holidays in the UK is relatively small compared to many other European countries. However, direct comparison is inaccurate since the 'substitute day' scheme of deferment does not apply in most European countries, where holidays that coincide with a weekend (29% of fixed-date holidays) are 'lost'.”

http://en.wikipedia.org/wiki/Bank_holiday

http://bank-holidays/info
http://bank-holidays/info/what-is-substittute-day

Bank holidays - are holidays when bank and many other businesses are closed for the DAY.

Public holidays - are holidays which have bees observed through custom and practice.

Substitute day - when the usual date of bank or public holiday falls on Sat. or Sund., a sudstitute day is given, NORMALLY the following Monday.