Count the days that actually count.

Ten days sounds simple until you try to pin it to a calendar. In almost every quote, contract and payment term in New Zealand, a "day" means a working day: Monday to Friday, minus public holidays. That is a very different thing from ten calendar days.

Say you promise a job in ten working days starting the first week of December. Count it on your fingers across weekends and the Christmas and New Year holidays and it can land in the third week of January. Same ten days, three weeks of real time. This is the single most common way trade timelines quietly blow out, and it is entirely avoidable if you count the right kind of day from the start.

New Zealand does something sensible with holidays that fall on a weekend. If Waitangi Day, ANZAC Day, Christmas Day or Boxing Day lands on a Saturday or Sunday, the day off moves to the next available weekday. That is mondayisation. The holiday is still marked on its real date, but the paid day off, the one where nobody is on the tools, shifts to a Monday or Tuesday.

It matters for counting because the day the work actually stops is the observed date, not the calendar date. This calculator uses the observed, mondayised dates for 2026 and 2027, so it removes the day people are genuinely off. Christmas 2026 is a good example: Boxing Day falls on a Saturday, so it is observed on Monday 28 December, and that Monday is the day the calculator treats as a holiday.

Some parts of the year are minefields. The run from Christmas to mid-January can swallow four separate public holidays, and that is before anyone takes annual leave on top. A job quoted in early December on a working-day basis can look like it is dragging when really the calendar is just thick with days off.

Easter is the other trap. Good Friday and Easter Monday are both public holidays, so a job spanning that weekend loses two working days in a single week. If you quote calendar days over Easter without thinking, you will overpromise. Run the dates through the calculator instead and quote the real number. Clients respect an honest date far more than an optimistic one you then miss.

Working days shape when money moves, not just when work finishes. Two payment terms dominate small business in New Zealand, and they behave very differently.

Net 7 days means payment is due seven days after the invoice date. Clean, fast, and good for cash flow, though whether those are calendar or working days should be spelled out on the invoice so there is no argument.

The 20th of the following month is the classic New Zealand trade term. Invoice any time in one month and payment is due on the 20th of the next. Invoice on the 2nd and you wait almost seven weeks. Invoice on the 28th and you wait three. The date you send the invoice quietly decides how long you wait to be paid, which is why sending invoices early in the month is one of the cheapest cash-flow wins there is.

Whichever terms you use, count the days properly. A due date that lands on a weekend or a public holiday often means the money does not clear until the next working day, so build that in rather than being surprised by it.

Two modes. Days between dates counts the working days from your start to your end, which is what you want for checking a contract window or a payment term. Add working days takes a start date and a number of working days and gives you the finish date, which is what you want when quoting a job. Either way it shows you which public holidays fell inside the range, so you can see exactly where the time went.