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Sleep Schedule Overlap Planner

Two people share one dark house, and the lights go off at two different times. That is not a scheduling detail. It decides whether you see each other at midnight or not at all. The Sleep Schedule Overlap Planner takes two pairs of times and draws you a single 24-hour map: when you are both asleep, when you are both awake, how long the morning window really is, and how much of the evening survives after the first person turns the light off. You also set two numbers that decide most of the outcome, namely how far you are willing to move your bedtime and how much shared time you actually want to protect. From those five inputs the planner works out three realistic bedtimes if one of you gives ground, what each move costs in sleep minutes, what a longer weekend would buy, and whether the current arrangement leaves anyone under seven hours on a work night. This is a self observation tool, not a professional assessment. It does not judge your sleep or your relationship. It turns two vague feelings about timing into a map you can argue with, and then into a schedule you can test on a Tuesday.

24-hour format, for example 23:30
24-hour format, for example 07:00
Times after midnight are fine, write 00:45
24-hour format, for example 06:15
h
The largest shift you would actually live with for a month
h
Hours together after the first alarm and before the first light off
days
The other days are treated as free nights
Result

How to use it

STEP 1

How to use this planner: enter the four times in 24-hour format, because 23:30 and 07:00 are far harder to misread than half past eleven. Use the time you actually get into bed, not the time you set the alarm, and the time you are genuinely up, not the time you wish you were up. Two honest numbers beat four precise ones.

STEP 2

Set your shift tolerance next. This is how far you are willing to move your own bedtime to meet the other person, and it decides which of the three options is even available to you. People usually guess high and then feel aggrieved, so pick a number you could genuinely live with for a month. Thirty minutes is the usual answer for shift workers, one hour is a normal answer for most couples.

STEP 3

Set the shared time you want to protect. This is the number of hours you want to be together after the first alarm and before the first light goes off, and two hours is a common answer. The planner then tells you which of those two windows your schedules already cover and which one falls short, and by exactly how many minutes.

STEP 4

Put your work days in last. The planner compares your weeknight sleep with a free night where both of you sleep one hour later, then averages the week. That average is the number that decides whether a weekend lie-in is genuinely rescuing the week or simply covering up a problem the other five nights still have.

Three common mistakes

  • The most common mistake is entering the time you set the alarm as your wake time. You are already awake for the ten minutes it takes to find the phone, and the person you live with is awake for those minutes too. Entering the alarm time invents a quarter of an hour of overlap and hides the real gap between the two morning windows.
  • Another common mistake is entering your ideal schedule instead of your real one. The planner is only as honest as the times you type, and an optimistic bedtime of 23:00 on a night you actually go to bed at 00:20 makes every other number on the page wrong. If you have to estimate, use the worst week you have had rather than the best.
  • Watch out for a bedtime that runs past midnight. A partner who goes to bed at 00:45 is not on the same clock as someone who goes to bed at 23:30, even though both look late in the evening. Crossing midnight changes which window comes first and which comes last, and the planner handles the wrap so that you do not have to.
  • Do not read a long overlap of sleep as a good sign. Being asleep at the same time is mostly a scheduling fact, and it is not a measure of how either of you is doing. This page is a self observation tool, not a professional assessment, so it never scores your nights. If one of you is regularly lying awake or sleeping through the day, take that to a doctor or a sleep specialist rather than to a calculator.

How the overlap is actually calculated

Each schedule is turned into two windows on a 24-hour circle. Your sleep window runs from your bedtime to your wake time and has a length of 1440 minus your sleep hours; your awake window is everything that is left. The planner then intersects the two sleep windows and the two awake windows separately, which is why the page reports two different numbers rather than one.

  • Both asleep is the overlap of the two sleep windows. It tells you how often one of you is going to be woken up by the other, and how much of the night is genuinely shared unconscious time.
  • Both awake is the overlap of the two awake windows, and it is the number that matters for planning. Two people with completely different bedtimes can still have fifteen hours of shared waking time, because everyone is awake for most of a day.
  • Share of a 24-hour day divides the shared awake time by 1440. A figure around 70 percent is normal for a couple with reasonably close schedules, and it should not surprise you.
  • The morning and pre-sleep windows are measured against the number of shared hours you asked for. The first one starts at the earlier of the two wake times, the second one ends at the earlier of the two bedtimes, so both windows are anchored on the person who has to move first.

One detail that catches people out: the gap between the two wake times is time one of you spends alone right after the alarm. If that gap is 45 minutes, someone is getting up, making coffee and reading the news alone every morning while the other person sleeps. That is usually the first thing worth fixing, and it costs nobody any sleep.

Reading the 24-hour map

The map is drawn in plain characters so that it can be read without a colour legend. Each block is 30 minutes and the line starts at midnight on the left, with the hour numbers running along the top. The first row is you, the second row is your partner, and the third row is the combined state of the two of you.

  • # means asleep and . means awake. Where the two rows line up, you can see exactly which part of the night you share without talking.
  • * marks the slots where both of you are asleep, and = marks the slots where both of you are awake. A run of dashes is a slot where exactly one person is awake, and those dashes are the expensive ones: they are the hours nobody can spend together.
  • The resolution is 30 minutes, so treat the boundaries as approximate. If your alarm is at 07:00, the block that starts at 06:45 is counted by its midpoint, and the map will place the change one block early or late.

What to look for is the longest dash run. On the default setup there is a stretch early in the morning where you are awake and your partner is not, which is the 45-minute wait before the shared window opens, and a stretch just after midnight where the reverse is true. Those two stretches are the whole problem, and they are visible without any arithmetic at all. Once you can see them, the rest of the page is simply a list of ways to move them.

Choosing who moves, and what it costs

The three options are the same three shapes every time. One of you moves all the way to the other bedtime, the other one moves all the way to yours, or both meet somewhere in between at midnight. The arithmetic is simple enough to do on paper: moving a bedtime 75 minutes later while the wake time stays put costs 75 minutes of sleep, and moving it earlier buys exactly the same 75 minutes back.

  • On the default setup the gap between the two bedtimes is 75 minutes, and each full move costs 1.25 h of sleep. With a one-hour tolerance, neither full move is actually available to you, which is worth knowing before you negotiate.
  • The midnight compromise costs you 30 minutes and your partner 45 minutes, and it is the only option inside a one-hour tolerance. Small compromises like this work better than big ones because neither person can tell, week to week, who gave up the half hour.
  • The weekend arithmetic is the cheapest fix available. Sleeping one hour later on two free nights returns 2 h a week to each person, and it costs nothing except the willingness to be the first one awake on Saturday.
  • The seven-hour reference is the one fixed point on the page. Your partner needs a 23:15 bedtime to reach seven hours, which is 90 minutes earlier than the current one. Whether that is possible is a different conversation, but at least it is now a specific number rather than a vague sense that something is off.

None of this is a verdict on anyone. It is a description of two time zones living in the same flat, and the fastest way to improve it is to move one number rather than to have a long conversation about effort.

FAQ

What if our bedtimes are more than four hours apart?
The map still works, but the useful output changes. When the bedtimes are far apart, the shared awake window shrinks and the dashes get long, and the three options stop being equally attractive because each full move now costs several hours of sleep. In that case the tool is most useful for two numbers: the shared awake hours, which tell you how much you actually have, and the seven-hour bedtime, which tells you what a fix would cost. A relationship where one person sleeps from 23:00 to 07:00 and the other from 01:00 to 09:00 has roughly five hours of shared waking time, and no amount of planning turns that into more than the day contains.
Does the planner tell us which of us has the problem?
No, and that is deliberate. The planner describes two schedules and the space between them, nothing about the people. It will tell you that one of you is sleeping 5.5 h and the other 7.5 h, and it will tell you that the pre-sleep window is fully covered while the morning window is 45 minutes short. Whether that pattern reflects a hard week, a new baby, a commute, or a preference for late nights is not something a page with seven inputs can know. Take the numbers to each other as descriptions of time, not as verdicts about effort, because they are the same thing.
What does the seven-hour reference actually mean?
It is a widely used reference point for adults and nothing more precise than that. The planner uses it because a seven-hour night gives you a clean comparison between the two schedules, and because it turns the vague feeling of not sleeping enough into a specific bedtime. It is not a clinical threshold, it does not account for the fact that some people need less sleep, and it says nothing about the quality of any night. If the number makes you worried about your own sleep, that is a good moment to talk to a doctor or a sleep specialist rather than to keep adjusting an alarm.
Can we use it if one of us works nights?
You can, but you should treat the result as a rough map rather than a schedule. The planner assumes one stable 24-hour cycle per person with a single sleep block, so a rotating shift pattern will look like two different people. A practical way to use it is to run it four times, once for each shift in the rotation, and compare the shared awake hours. If your rotation includes three nights where the shared figure drops below two hours, that is worth designing around: choose the one night in the rotation where you do not need to cover each other, and protect that one rather than trying to fix all four.
Is the map accurate enough to plan a real evening around?
Yes, provided you enter the times you actually keep rather than the times you intend to keep. The resolution is 30 minutes, so the map will not tell you whether the last half hour of the evening is worth keeping, but it will reliably tell you whether you have two hours together after dinner or none at all. The most useful thing it produces is the pre-sleep window row: if that shows 2.0 h against a 2.0 h target, you can put something in the calendar on Tuesday and know that the time exists.

Limits of this tool

  • This is a self observation tool, not a professional assessment. It calculates times and never rates a relationship, a person, or a night of sleep.
  • Limits: it assumes one constant schedule per person, one 24-hour cycle, and no naps, night shifts, or travel across time zones. It is not a sleep tracker.
  • Not for: diagnosing insomnia, sleep apnoea, or any other sleep condition, and this page cannot see how you actually sleep. If sleep problems persist, talk to a doctor or a sleep specialist.
  • The seven-hour figure is a shared reference point for adults, not a clinical threshold for you. Use the numbers as a map to discuss together, never as a score.