An employee who has worked continuously for one full year shall be entitled to an annual holiday of not less than six working days which shall be in advance by the employer or set out in an agreement made between the employer and the employeeIn subsequent years,the employer may fix an annual vacation for the employees of more than six working days.The employer and employee may agree in advance that the annual vacation be cumulative and postponed and taken together with that of the following year.For an employee who has worked for less than one year,the employer may fix an annual vacation proportionately