FMLA Rolling 12-Month Period: Shifting Window and Intermittent Leave

The FMLA rolling 12-month period is a look-back method: on any day you take leave, your employer looks at the previous 12 months, adds up every FMLA day you already used in that window, and subtracts it from your 12-week entitlement. Whatever is left is what you have available that day. The window moves forward one day at a time, so as older leave usage passes its 12-month anniversary, it drops off the calculation and your balance slowly refills.

How the Shifting Window Works

Federal regulations give employers four ways to define the 12-month period that caps your leave. The rolling method, at 29 CFR 825.200(b)(4), is the only one measured backward from the date you actually use leave rather than tied to a calendar year or a fixed anniversary.¹

Picture a spotlight covering the 12 months immediately behind today. Any FMLA leave inside that spotlight counts against your 12 weeks. Anything older is invisible to the calculation. Tomorrow the spotlight moves one day forward, and whatever day just aged past the 12-month mark stops counting.

That’s the whole mechanism, and it’s the reason employers tend to prefer it. Under a calendar-year approach, you could take 12 straight weeks in November and December and start a fresh 12 weeks on January 1, producing 24 consecutive weeks of leave.² The rolling look-back makes that stacking impossible: you can never exceed 12 weeks in any consecutive 12-month stretch.

Calculating Your Available Leave

Start with 12 weeks. Subtract every FMLA day you used in the prior 12 months. That’s your current balance.

The Department of Labor’s own regulation example is worth walking through. An employee takes four weeks starting February 1, another four weeks starting June 1, and a final four weeks starting December 1. That uses the full 12-week entitlement. The employee has zero leave available until February 1 of the following year, when the earliest batch of four weeks starts falling outside the look-back window. From that point, the balance refills at the same rate it was originally used, one day at a time over four weeks.³

A simpler case: you took three weeks of FMLA leave seven months ago and nothing since. You have nine weeks available today. Those three used weeks will stay in your window for another five months. As each of those days hits its 12-month anniversary, your balance ticks up.

Precise records matter more here than with a fixed-year method, because the available balance can change daily. Most employers use payroll or HR software to store exact usage dates and recompute the remaining balance automatically.

Variable Schedules

If your hours change from week to week, your employer may not be able to say exactly how many hours you would have worked during a leave week. The Department of Labor allows the employer to use a weekly average built from the 12 months of scheduled hours before your leave began, including weeks when you used other types of leave.⁴

Holidays and Shutdowns

A holiday inside a partial leave week doesn’t count against your balance unless you were scheduled to work that day and used FMLA for it. A holiday inside a full FMLA week counts as part of the week. Business shutdowns work the same way. If the business closes for a full week and no one is expected to work, those days don’t count against your FMLA. If the closure is partial and you’re taking leave in daily or hourly increments, the closed days shouldn’t be deducted either. The only time a partial-week closure still costs you a full FMLA week is when you were already taking the entire week off.⁵

Intermittent Leave Under the Rolling Method

Intermittent leave is where the rolling method gets administratively intense. Every hour or partial day you take triggers a fresh look-back calculation. A chronic condition that requires two days off a month produces a new snapshot every absence.

The upside is that your balance also replenishes incrementally. Each small absence ages out of the window on its own 12-month anniversary, and the used time becomes available again. That’s why accurate tracking down to the hour, or even the minute, matters so much with intermittent leave.

Your employer has to track FMLA leave using the smallest time increment it uses for any other type of leave, and never in increments larger than one hour. If sick leave is tracked in 15-minute blocks, FMLA is tracked in 15-minute blocks too. Your employer also can’t force you to take more FMLA leave than you actually need. A 90-minute appointment can’t be rounded up to a half-day.⁶

One exception: when it’s physically impossible for you to start or stop work mid-shift, such as a flight attendant mid-flight or a technician sealed in a clean room, the entire forced absence counts as FMLA leave.⁶

Mandatory vs. Voluntary Overtime

If your employer requires overtime and you can’t work those hours because of your FMLA condition, the missed mandatory overtime counts against your FMLA balance. Voluntary overtime you skip does not.⁴ This catches people off guard. In a workplace with routine mandatory overtime, your 12 weeks can drain faster than your regular schedule alone would suggest.

Finding Out Which Method Your Employer Uses

An employer must pick one method and apply it uniformly to every employee. Different methods for different workers, or a different method for a specific leave request, isn’t allowed.⁷

The method is typically listed on Form WH-381, the Eligibility and Rights and Responsibilities notice your employer gives you when you request leave. That form has a checkbox identifying which of the four methods applies at your workplace.⁸

Switching methods requires at least 60 days’ advance notice to all employees, and during the transition whichever method gives you more leave is the one that applies. That rule blocks an employer from strategically switching right when you file a request.⁷ If an employer never formally selects a method, the Department of Labor defaults to whichever option gives the employee the most leave.¹

Two Situations the Rolling Method Doesn’t Cover the Same Way

Military caregiver leave is not on the rolling clock. If you’re caring for a covered servicemember with a serious injury or illness, the entitlement rises to 26 workweeks, and that leave always uses a single 12-month period measured forward from the first day you take it, regardless of which method your employer picked for standard FMLA.³ During that forward-measured year, you’re capped at 26 workweeks combined for all FMLA reasons, with no more than 12 of those weeks used for standard qualifying reasons.⁹

Spouses at the same employer share some of the entitlement. For the birth or placement of a child, or to care for a parent with a serious health condition, both spouses together are limited to 12 workweeks total during the applicable leave year, not 12 each. The rolling look-back applies to that shared cap the same way it applies to an individual’s leave. Each spouse still keeps a full individual 12-week entitlement for their own serious health condition, to care for a sick spouse or child, or for a qualifying military exigency.¹⁰

1
eCFR. 29 CFR 825.200 – Amount of Leave
2
U.S. Department of Labor. Fact Sheet 28H – 12-Month Period Under the Family and Medical Leave Act
3
eCFR. 29 CFR 825.200 – Amount of Leave
4
U.S. Department of Labor. Fact Sheet 28I – Counting Leave Use Under the Family and Medical Leave Act
5
U.S. Department of Labor. FMLA2026-1 Opinion Letter
6
eCFR. 29 CFR 825.205 – Increments of FMLA Leave for Intermittent or Reduced Schedule Leave
7
eCFR. 29 CFR 825.200 – Amount of Leave
8
U.S. Department of Labor. Notice of Eligibility and Rights and Responsibilities
9
U.S. Department of Labor. Fact Sheet 28M(a) – Military Caregiver Leave for a Current Servicemember Under the Family and Medical Leave Act
10
U.S. Department of Labor. Fact Sheet 28L – Leave Under the Family and Medical Leave Act When You and Your Spouse Work for the Same Employer