FMLA Insights describes a 12-month rolling period as one that starts on a significant day of the year, such as an employee's hire date, rather than on Jan. 1. A rolling 12-month period is often used to calculate an employee's leave accrual and can be a different date for each employee in a company.
According to FMLA Insights, a rolling 12-month period often counts backwards when being used to calculate the amount of leave an employee has accumulated. If an employee has four weeks of leave per year and uses one day on March 23 and another day on July 3, a day of leave is added to the employee's available paid leave time on the year anniversary of each date. If the employee requests leave and the human resources department sees that, as of the date the employee wants to take the leave, four weeks have already been taken during the previous 12 months, the employee is ineligible to take time off from work. A rolling 12-month period helps companies ensure that employees are not taking more time off of work than they are entitled.
Schiff Hardin LLP notes that when an employer uses a 12-month rolling period, each employee's available leave balance is updated daily. An employee who takes more leave than allotted during the rolling 12-month period can be subject to reprimand depending on the attendance policy of the company.