Even or Odd Weekend: How to Know Which Is Yours, and the January 2027 Trap
A weekend takes the parity of its week: Saturday and Sunday belong to the week that started on the Monday before. The weekend of October 3 and 4, 2026 is therefore even, and the one of October 10 and 11 is odd. One exception to watch for: in early January 2027, two odd weekends happen back to back.
Published on August 26, 2026 · updated on October 1, 2026
Is this week even or odd?"Every other weekend," the court order says, sometimes "even weekends." To know whether a weekend is even or odd, look at its week number. Saturday and Sunday are the last two days of the week that began on Monday: an even weekend is one that falls in an even week. There's no gray area, except once every five or six years, and this winter is one of those times.
Even or odd weekend: the rule for figuring it out
Week numbers follow the ISO 8601 standard, the one used by digital calendars, schools, and businesses across Europe. It comes down to two rules:
- a week runs from Monday to Sunday;
- week 1 of a year is the one that contains the year's first Thursday, meaning the week with at least four days in the new year.
The first rule is all you need for weekends. Saturday, October 10, and Sunday, October 11, 2026, fall in week 41: that's an odd weekend, from Saturday morning through Sunday night.
To check it yourself, a spreadsheet will do: =ISOWEEKNUM(TODAY()).
On a phone, week numbers are hidden by default: in Google Calendar, the option is
in the display settings; on an iPhone, it's under Settings, then Calendar.
Why two calendars can give different numbers
Most disagreements come from here. Part of the world starts its week on Sunday, and many calendar apps, spreadsheets, and printed calendars default to that setting.
In a calendar that starts on Sunday, the Sunday of a weekend slips into the following week. The same weekend ends up split across two numbers, and two parents each checking their own phone get two different answers for the same Saturday. Before arguing about it, check that both calendars display weeks running Monday through Sunday. That usually settles it.
"Every other weekend" doesn't say which one
Many agreements say "every other weekend" without mentioning parity. In that case, everything starts from the first weekend spent at the receiving parent's home, and the rest follows from there. Write that date down the same day: three years later, no one remembers it for sure.
Even weekends aren't reserved for the father or the mother by any convention. Both halves are equal, and over a year they share long weekends in a comparable way.
The trap: two odd weekends in a row in January 2027
A year usually has 52 weeks. 2026 has 53, because January 1, 2026, fell on a Thursday. The extra week goes unnoticed all year, then shows up all at once at the turn of 2027.
| Weekend | Week | Parity |
|---|---|---|
| December 26 and 27, 2026 | 52 of 2026 | even |
| January 2 and 3, 2027 | 53 of 2026 | odd |
| January 9 and 10, 2027 | 1 of 2027 | odd |
| January 16 and 17, 2027 | 2 of 2027 | even |
The weekend of January 2 and 3, 2027, still belongs to week 53 of 2026. Two odd weekends follow each other, and the even-weekend parent waits three weeks between December 27 and January 16.
Take Nadia, who has had her daughter on even weekends since the start of the school year. She has her on December 26 and 27, expects her again on January 9 and 10 as usual, and finds out the Wednesday before that it's actually an odd weekend. The court order was followed to the letter, no one cheated, and the argument starts anyway.
The same thing happened at the end of 2020 and will happen again at the end of 2032. It always lands in the same spot: the holiday season, which many court orders already handle separately.
What you can do
- Check the holiday-season clause first. If it covers this period, it usually overrides the regular weekend rotation, leaving only the January 9 and 10 weekend to settle.
- Agree on a swap in writing, in November rather than the night before. A dated message, kept by both parents, is enough.
- Leave it as is and note that the gap will even out over time. That's a valid choice too, as long as it's made in advance.
The full week-by-week breakdown for 2026 and 2027 is in even or odd week, the complete rule.
Counting weekends doesn't tell you who got how much time
Two parents alternating weekends almost never end up with the same number of nights. A weekend can start Friday evening or Saturday morning, holidays follow a different rule, and a one-off swap often only gets written down on one side. The night is the only unit that counts without an argument.
I built Nestido to keep our own schedule. You describe your rhythm once, "every other weekend" included, and the following months fill themselves in; all you note afterward are the swaps, and the other parent sees the same calendar. If your arrangement follows even or odd weekends, choose “Even / odd weekends”: this schedule follows the ISO week number of the Saturday, including the change from week 53 to week 1. Under this basic schedule, both weekends, January 2 and 3 and January 9 and 10, 2027, go to the parent who has odd weekends; holidays and one-off swaps are recorded separately. “Every other weekend” remains a separate option: it alternates without following the week number. To choose a rhythm, see which custody rhythm to choose; for the night count, counting nights without arguing.