A leave period usually a year but can be different according to company HR processes. Leave periods can’t overlap, which means if an employee applied for annual leaves in the leave period for “Year 2014”, his leave balance in the leave period “Year 2015” won’t get affected. This is the same for all types of leaves. Also if the leave period for the year 2015 is not defined, employees won’t be able to apply leaves for 2015.