Japanese Business Day Calculator
Work out business days in Japan with weekends and public holidays excluded — including substitute holidays. Find the date N business days out, or count the business days in a range. Everything runs in your browser; your dates are never sent anywhere.
Your dates are processed entirely in your browser and are never sent anywhere.
Enter your conditions above and select Calculate.
- Result
- Business days
- Calendar days
Days excluded
No days were excluded.
There were too many excluded days to list, so only the first 200 are shown.
| Date | Reason |
|---|
How to use
- Pick what you want to calculate: a date N business days after or before, or the number of business days in a range.
- Enter the start date and the number of business days (or the end date). Adjust the non-working days or start-date rule if you need to.
- Select Calculate. Every excluded day is listed with its holiday name, so you can check the result against your own calendar.
How it works
What counts as a business day
A day is counted as a business day unless it falls into one of these:
- A non-working weekday (Saturday and Sunday by default)
- A Japanese public holiday, when "Exclude public holidays" is on
Where the holiday data comes from
This tool uses the CSV that Japan's Cabinet Office publishes for national holidays, exactly as published.
The important part is that substitute holidays and "citizens' holidays" are already in that file. For example, 6 May 2026 appears in it as a substitute for Constitution Memorial Day, which fell on a Sunday that year. So does 22 September 2026, the citizens' holiday that sits between Respect for the Aged Day and the Autumn Equinox.
Because of that, this tool does not work out substitute holidays on its own. Doing so would risk counting a day twice, or disagreeing with the official list. The published data is treated as the single source of truth.
Why the date range is limited
The spring and autumn equinox holidays are set by astronomical calculation and are only fixed in law when they're published in the official gazette the February before. That means the Cabinet Office file itself only reaches so far into the future.
Dates beyond that range produce an error rather than a result. For deadline work, the worst possible outcome is a wrong date presented as a correct one, so the tool says when it can't answer instead of guessing.
Whether the start date counts
By default it doesn't. Article 140 of the Japanese Civil Code states that the first day of a period is not counted, and that's the general rule.
Contracts sometimes override this by saying the count starts on the day itself. When that applies, turn on "Count the start date itself". A single day's difference changes the deadline, so it's worth confirming which rule you're calculating under.
Why excluded days are listed
You can't tell whether a business-day calculation is right just by looking at the resulting date. Seeing which days were removed, and why, lets you check it against a calendar. Holidays are shown by name.
FAQ
Does this tool send my dates anywhere?
No. The holiday data is bundled into the page, and the calculation happens entirely in your browser. Once the page has loaded there is no further network traffic, so it works offline too.
Are substitute holidays taken into account?
Yes. The Cabinet Office CSV already contains substitute holidays and citizens' holidays, and this tool uses that file as published. So 6 May 2026 (the substitute for Constitution Memorial Day) and 22 September 2026 (the citizens' holiday between two others) are both correctly excluded.
I got a message saying the date is outside the range.
That appears when you pick a date beyond the years covered by the holiday data. The equinox holidays are only fixed in the official gazette the February before, so the published file has an end point. The tool won't guess past it — presenting a wrong date as correct is the worst failure mode for deadline work.
Is the start date included in the count?
Not by default. This follows Article 140 of the Japanese Civil Code, under which the first day of a period isn't counted. If your contract says the count starts on the day itself, turn on "Count the start date itself". One day's difference changes the deadline, so the setting is shown alongside the result.
Can I use non-working days other than Saturday and Sunday?
Yes. You can pick any combination under "Non-working days", which covers cases like a Wednesday closure or Sunday-only closing. Clear them all and you'll get a count that excludes public holidays only.
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