The FMLA, or Family and Medical Leave Act, is a federal law that allows certain employees working for covered employers to take up to 12 weeks of unpaid leave during each 12-month period. The 12-week allowance resets every 12 months, so in a sense, FMLA continues each year. The FMLA does not necessarily work on a calendar year to calendar year basis, though. Federal regulations allow employers to choose one of four different methods for measuring the 12-month period for FMLA coverage.

Calendar Year

One of the easiest methods by which an employer can track FMLA leave is to place all employees on a calendar year track. This means that each employee can take 12 weeks of FMLA leave anytime between January and December, and the calculations reset on January 1 of each year. One reason employers may not like the calendar year method is that an employee could end up with 24 consecutive weeks of FMLA leave if the employee takes the last two weeks of December and the first two weeks of January.

Fixed Period

Similar to the calendar year method, an employer can instead choose to measure FMLA leave by any fixed 12-month period. For example, an employer could measure FMLA leave from March 15 of one year to March 14 of the next year. The effects are the same as for a calendar year method except that the new year does not necessarily start each January 1.

Employee Leave Initiation

Employers can calculate the 12-month FMLA period differently for each employee by starting each 12-month period whenever an employee takes FMLA leave. The 12-month period begins on the first day an employee takes FMLA leave. Basically, this method ensures that an employee who takes FMLA leave must then wait another 12 months before taking more FMLA leave, so there is no risk of 24 consecutive months as there is with the first two methods using a fixed 12-month period.

Rolling Period

The final calculation method is a rolling 12-month period that measures backward from the date that each employee uses FMLA leave. This is very similar to the third method where an employee's first day of leave initiates a 12-month period, except that, under this fourth method, the employer looks backward instead of forward. When an employee wants to take FMLA leave, the employer counts backward from that date and measures the amount of leave already taken in the previous 12 months.

Employee Choice

If an employer does not create a set policy electing one of the four methods above, then each employee has the right to choose the calculation method he prefers.