Forty-eight hours on duty, then ninety-six off, on a six-day cycle. Two full days at the station back to back, then four days clear. The two on-duty days are identical in structure, which is why the engine builds one shift-day type and applies it to both.
These are example times, not your times. Everything below is computed from a single pair of wake anchors: 6:30 AM on a work day and 8:00 AM on a rest day. A 6:30 AM wake puts you at an 0830 shift change, and an 8:00 AM rest-day anchor is about as late as the four days off can drift without leaving a gap to close before the next 48. If your anchors are different, every window below shifts with them, which is what the plan builder does with your own numbers.
The plan works backward from the wake anchor rather than forward from bedtime, because bedtime is the part your schedule takes away from you. The sleep target on each day is the anchor minus the sleep opportunity; the caffeine cutoff is eight hours before that target; the last real meal is three hours before wind-down starts. So the anchor is the only number you set, and the rest falls out of it.
Each of the two days on duty. 24 hours on duty, going on the tour at 8:30 AM.
| Wake anchor | 6:30 AM |
|---|---|
| Bright light | 6:30 AM to 8:00 AM |
| Caffeine | 7:30 AM to 8:00 AM (first cup), stop by 2:30 PM |
| Planned nap | 10:30 AM to 12:00 PM |
| Last real meal | by 6:00 PM |
| Wind-down | 9:00 PM to 9:30 PM |
| Sleep target | 10:30 PM |
The day you come off the second 24.
| Wake anchor | 6:30 AM |
|---|---|
| Bright light | 6:30 AM to 8:00 AM |
| Caffeine | 7:30 AM to 8:00 AM (first cup), stop by 3:30 PM |
| Planned nap | 10:30 AM to 12:00 PM |
| Last real meal | by 7:00 PM |
| Wind-down | 10:00 PM to 10:30 PM |
| Sleep target | 11:30 PM |
The remaining days of the 96.
| Wake anchor | 8:00 AM |
|---|---|
| Bright light | 8:00 AM to 9:30 AM |
| Caffeine | 9:00 AM to 9:30 AM (first cup), stop by 4:00 PM |
| Last real meal | by 7:30 PM |
| Wind-down | 10:30 PM to 11:00 PM |
| Sleep target | 12:00 AM |
Forty-eight hours on duty means two sleep opportunities you do not control, one after another, and the second is the one that goes badly — you enter it already short. There is no version of a 48 where the plan produces good sleep on the second night, so the plan is damage control: every horizontal opportunity taken, and the caffeine cutoff held even when it is the second night and the cutoff feels absurd. The other half is the ninety-six. Four clear days is long enough that the anchor drifts later a bit each day if nothing holds it, and the last day off is what you take into the next 48. The engine keeps the day off the 48 as its own recovery type, aligned to the shift anchor, rather than treating it as the first day of the break.
Sleep on a 48 is interrupted sleep by definition, so the plan is damage control: take every horizontal opportunity, keep caffeine on the cutoff even when the second night feels impossible, and treat the first day off as recovery rather than the start of the break. Once you are past that day, the 96 is long enough to genuinely reset - hold the rest-day anchor rather than drifting later across four days.
Eight hours before the sleep opportunity you are protecting. In the worked example on this page, a 6:30 AM wake anchor on a work day puts the sleep target at 10:30 PM, so the last caffeine of any kind lands at 2:30 PM. Move the anchor and the cutoff moves with it — the eight hours is the rule, not the clock time.
The plan sets the sleep target backward from the wake anchor rather than forward from the end of a shift. In the example here, a 6:30 AM work-day anchor gives a 10:30 PM sleep target, with wind-down starting at 9:00 PM. On a rest day the 8:00 AM anchor gives a 12:00 AM target.
Within 90 minutes of waking, whatever the sun is doing. In the worked example that is 6:30 AM to 8:00 AM on a work day. Ten to fifteen minutes is enough. Then keep bright light off you in the three hours before the sleep target.
One nap, taken on purpose, four to five and a half hours after waking — 10:30 AM to 12:00 PM in the worked example on this page. Twenty to thirty minutes, or a full ninety. Anything in between leaves you groggy.
Recovery day (off the 48) is planned as its own kind of day rather than a normal one. In the example, it runs on a shorter sleep opportunity ending at 6:30 AM, with the caffeine cutoff at 3:30 PM and the last real meal by 7:00 PM.
The plan builder takes six questions — your pattern, your two wake times, your last cup of coffee — and computes the same windows against the schedule you actually work, as a visual timeline for each kind of day. Free, printable, no account.
Build my free sleep planEvery window on this page comes from one of a handful of rules, and the Shift Worker's Field Manual is where those rules are laid out with their sources: why the wake anchor is the lever rather than bedtime, what light does to the body clock and when, the eight-hour caffeine cutoff and where it comes from, and what to do when the problem is bigger than a schedule.
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