See a custody schedule on a calendar, and count the overnights

Overnights, not hours, and not days. Almost every jurisdiction that attaches anything to parenting time — the label on the arrangement, a child-support formula, which parent the school writes to — counts where the child sleeps, which is why a schedule is described as a number of nights and why a "day" in a parenting plan is really the night at the end of it.

The headline figure is taken over one full cycle rather than over the months on screen, and that is the one thing on this page worth being pedantic about. A printed range almost never contains a whole number of fortnights, so the same 2-2-3 comes out as 50 percent over fourteen months and 51.6 percent over three. Quote the second number in front of a judge and you are quoting an artefact of how many months you happened to print.

The nights-a-year figure is the cycle share applied to 365, before any holiday schedule. That matters more than it sounds: a fortnight that divides evenly can end up well away from even once a summer block and an alternating Christmas are written in, and almost every plan lets the holiday schedule override the ordinary one.

The pattern is pinned to a change-over weekday, and the calendar snaps back to the most recent one on or before the date you give it. That is deliberate. A schedule that has been running since March is not restarting on the day you open a calculator; you are looking in on a cycle already in progress, and the sheet has to agree with the one on the other parent's fridge.

For the three every-other-weekend patterns the change-over day is fixed to Monday and the control is greyed out, because those shapes are defined by the calendar weekend. An "every other weekend" whose weekend fell on a Tuesday would be a different arrangement wearing the same name.

Swap which parent holds the first block and the whole calendar mirrors. On the even patterns that is cosmetic; on the every-other-weekend ones it decides which parent has most of the nights, so it is worth checking before printing.

Print gives you the calendars and the counts and nothing else — no page heading, no form, no site navigation. The tints survive the printer, and every square carries the parent's name as well as its colour, so a photocopy in black and white still reads and nobody has to rely on telling two pale shades apart.

Copy as text gives the same schedule as stretches of nights — "Ana, 1 to 2 September, 2 nights" — which is the shape a parenting plan is written in and the shape that pastes into a message without turning into a wall of dates.

The link carries the whole thing after the "#". Send it to the other parent and they see the same calendar, editable, with nothing stored on our side and no account at either end.

A printed month is a picture of an agreement. It is not the agreement, it keeps no record of what changed, and it cannot settle an argument about what was agreed in April — which is where co-parenting coordination actually goes wrong.

The Co-parenting app is the same schedule as a record. Once both parents have joined, each child's standing schedule takes effect only when both countersign it, every agreed version is kept, and one-off swaps go through the same countersign, with their terms frozen server-side at the moment both sides approve. Custody days are worked out on the server from what was agreed and flow to the shared calendar, so nobody is reading a picture.

It runs in a co-parenting space that sits between two private households: each parent keeps their own home, their own calendar and their own finances, and the space holds only the schedule, the kids' expenses, the shared records and messages that cannot be edited or deleted. It offers every pattern on this page by the same name this page uses, and anything else — a six-day rotation, a schedule built around shift work — as a day-by-day cycle you enter once and, once both have joined, both parents sign.

The names carrying their nights is deliberate on both sides. "Every other weekend" and "alternating weekends" are the same phrase to most people and get used for both the two-night and the three-night shape, and the difference between them is half again as many overnights. That is a bad thing to discover after two parents have countersigned it, so neither name appears in either place without saying which one it is.

• Co-Parenting
• Calendar
• Family Records
• Expense Splitter

Every app in the library is included with the household plan. This page stays free either way.

• 2-2-3, 2-2-5-5, alternating weeks: the custody schedules, explained
• What information should co-parents share, and what should remain private?
• Splitting the kids' expenses between two households without fighting
• Split shared expenses and see who pays who
• A phone and screen-time contract you can both actually sign
• Name the invisible work, then see who is actually holding it
• Make a printable chore chart for your family