Zerdly

Parenting Nights Per Year Calculator

Turn a weekly or alternating-week parenting schedule, plus dated holiday changes, into real nights per year and percentage of nights. Runs in your browser.

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How to use this calculator

Your routine

1600–9999. Every real date from 1 January to 31 December is counted.

Routine

Tick the nights the child sleeps at your home, named by the evening the night starts.

Your nights each week

This only changes which year and month a night near a boundary is counted in.

Holidays and one-off changes (0)

Overrides beat the routine. Dates are the evening each night starts; leave “to” blank for a single night.

Your schedule stays in this page only — nothing is stored or sent. Saving a file is your choice.

Choose your nights and press Calculate.

Or load the example to see a worked year.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the year (1600–9999) and choose a routine: the same nights every week, or alternating week A / week B with a date that falls in a week A.
  2. Tick the nights the child sleeps at your home, named by the evening each night starts.
  3. Optionally add holidays or one-off changes as dated overrides — they beat the routine. If two overrides disagree about a night you must choose how to resolve it.
  4. Press Calculate for your nights, the percentage of the year, monthly and weekday totals, a year calendar, and CSV or calendar (.ics) downloads.

How it works

Every real date from 1 January to 31 December is enumerated with date-only arithmetic (integer day numbers, so daylight saving can never shift a date). Each night is assigned to the date it starts — or, if you choose, the morning it ends.

Routine first, then overrides: nights = count of dates assigned to you; percentage = nights ÷ nights in the year (365 or 366) × 100. A repeated override for the same night counts once.

This is schedule arithmetic only. It does not apply any care band, child-support rule or legal test, and your schedule stays in the page unless you download a file.

Worked example

Friday and Saturday nights, 2026 and 2028. 2026 has 52 Fridays and 52 Saturdays: 104 nights ÷ 365 × 100 = 28.4932% (28.493150685…). 2028 is a leap year that starts on a Saturday, so it has 53 Saturdays: 105 nights out of 366 (28.6885%).

Frequently asked questions

Which date owns overnight care?

By default a night belongs to the date it starts — Friday night is the night that begins on Friday evening. You can switch to the date it ends (the morning). The choice only matters at the edges: it decides whether the night of 31 December counts in this year or the next.

How are holidays applied?

Add each holiday or swap as a dated override (a single night or a range). Overrides take precedence over the weekly routine. Identical overrides for the same night count once; if two overrides give the same night to different parents the calculator stops until you fix the rows or choose “the later row wins”.

Does this determine legal care percentage?

No. It counts nights on a calendar. Care assessments, court orders and child-support agencies apply their own rules and evidence, so use this as a planning figure only.

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Cite this tool

Zerdly. (2026). Parenting Nights Per Year Calculator. Retrieved from https://www.zerdly.com/tools/parenting-nights-per-year-calculator/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.