Use of Vacation and Holiday Credits. The use of vacation and holiday credits shall be in accordance with the guidelines set forth by the Chief. Vacation and holiday credits may not be carried over from one vacation year to another without the written approval of the Chief and the Mayor, with the following exception: In addition to “odd vacation hours” constituting less than a twenty-four hour carryover, members may choose to carryover, on the books, one additional twenty-four hour period from their regular vacation and holiday accrual, for use as a “floating day off.” This floating day off may be used at any time during the vacation year, providing that an existing vacation slot is available and providing that the member request the use of said floating day off at least six (6) calendar days in advance. At the option of the member, accrued compensatory time may be used in lieu of vacation or holiday accrual for the “floating day off.”