How to Read Your A/B/C Platoon Rotation

A three-platoon department splits its firefighters into three crews, usually called A, B, and C shift (some places use 1, 2, 3 or colors). At any moment one platoon is on duty, and the other two are off. The three take turns so the station is staffed 24 hours a day, 365 days a year, without anyone living at work.

That is the whole idea behind A/B/C. It is not a ranking or a station assignment. It is which of the three rotating crews you belong to, and it determines which days you work.

Most three-platoon departments run a 24/48 pattern: each platoon works a 24-hour shift, then is off for 48 hours while the other two rotate through. Because there are three crews and a three-day cycle, the schedule lines up cleanly. If A works today, B works tomorrow, C works the day after, and then it is A again.

A 48/96 department works the same three-crew idea with a longer block: a platoon works a 48-hour tour, then takes 96 hours off. Either way, the calendar is just those three crews marching through the days in order.

The colored squares on a firehouse calendar are shorthand for the platoons. A common scheme is red for A shift, black for B shift, and blue for C shift, though every department picks its own colors. Each day on the calendar is filled with the color of whichever platoon is on duty that day.

Once you know your color, reading the calendar is fast. Find today, note whose color it is, and you know who is on. Scan down the week and you can see your next tour and your next stretch off without counting. The colors are doing the same job as the letters, just faster for your eye.

The rotation is pure arithmetic, which is why you can project it as far out as you want. Pick any one day you know for certain (a shift you actually worked), and every other day follows by stepping through A, B, C in order. On a 24/48 the crew advances by one each calendar day. On a 48/96 a crew holds two days, then the next crew picks up.

This is also why an anchor date matters. Give a calculator one recent on-duty date for your platoon and it can phase the entire pattern correctly, then tell you who is on for any date, months or years ahead. No wall calendar required, and no miscounting when the month rolls over.

Two things complicate the clean A/B/C march. Kelly days remove a tour from a platoon periodically to trim average hours, so occasionally the crew you expected on a given day has a scheduled day off and coverage shifts. And trades move individuals between days without moving the whole platoon, so the person on the truck may not match the platoon color even when the crew does.

Neither breaks the underlying rotation. The three-crew cycle still runs; Kelly days and trades just sit on top of it. If you can read the base pattern first, the exceptions are easy to spot, because they are the squares that do not match what the rotation predicts.