Three 24-hour tours separated by single days off, then a four-day break, on a nine-day cycle: on, off, on, off, on, then four off. The single days between tours are the defining feature. You are never more than a day away from the next shift change until the break arrives.
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; the 8:00 AM rest anchor is for the four-day break, which is the only stretch long enough to hold a different one. 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 24 in the Kelly cycle. 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 one day between two 24s.
| 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 four-day break at the end of the cycle.
| 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 |
A single day between two 24s is not a break, and the structure will not let it be one. You come off duty in the morning, and the next shift change is the following morning — so the sleep opportunity in between is the only one you get, and it has to leave you fit for another twenty-four hours. That is why the engine treats those single days as recovery rather than rest: a shorter sleep held near the shift-day anchor and an early night, not a lie-in. The four-day break is the only place in the cycle where a rest-day anchor has room to hold for more than one day, and it is also where the whole thing can be undone by drifting three hours later across four days.
A Kelly cycle gives you one day between 24s. That day is recovery, not a break: keep the anchor near your shift-day anchor, take the nap, and go to bed early. Save the rest-day anchor for the four-day break at the end, where a real shift back toward a normal schedule can actually hold.
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.
Single day off between shifts 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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