Can I also set my company's own holidays?

In the initial state, only official holidays in Japan are supported, but by checking 'Add company special holidays' and entering the date, you can also calculate your own holidays.

How many years into the future can you calculate?

Future holidays will be automatically calculated based on the holiday law. The dates of the vernal and autumnal equinoxes are approximated using astronomical calculations until 2099.

Will the data be sent to the server?

No. All calculations are completed within the browser, so no data is sent to an external server.

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business day calc,

Business Day Calculator

Calculate X business days after/before a date, or count business days between dates.
Supports all 16 Japanese national holidays with auto-detection.

📱️

Japan Holidays

All 16 holidays auto-detected

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3 Modes

After, Before, and Count

Calculate X business days after/before a date instantly. Includes all 16 Japanese national holidays (Happy Monday, substitute holidays) with auto-detection. Supports Obon/New Year exclusion and custom company holidays.

Start Date

Business Days

days

about,

About

This is an online tool that calculates the number of business days from a specified date. Automatically takes Japanese holidays into account and counts business days excluding Saturdays, Sundays, and holidays.

Supports calculation of the number of business days between the start date and end date, and the calculation of the date ○ business days after the specified date. Ideal for delivery date management and schedule planning.

All processing is completed within the browser and no data is sent to the server.

how to,

How to Use

STEP 1

Set start date

Select a base (start) date from the calendar or press the Today button.

STEP 2

Enter the number of business days

Input the number of business days you want to calculate (or specify an end date in "Count" mode) and adjust your exclusion settings if necessary.

STEP 3

Check results

The number of business days and applicable dates are displayed. You can also see details about holidays and business closures.

glossary,

Glossary

Business Day: A working day when businesses are typically open. In Japan, this generally means Monday through Friday, excluding national holidays and special observances.
Non-business Day: Weekends, public holidays, and custom designated off-days (like company anniversaries or winter breaks) that are excluded from working day calculations.
National Holidays (Shukujitsu): Legally mandated public holidays in Japan. The tool automatically factors in dynamic dates, substitute holidays, and "Citizens' Holidays."
Start Date (Base Date): The date from which calculations begin. Knowing whether to include or exclude the start date ("Day 0" vs "Day 1") is critical for accurate deadlines.
Substitute Holiday (Furikae Kyujitsu): In Japan, if a national holiday falls on a Sunday, the immediate following working day becomes a statutory public holiday. The algorithm accounts for this.
Lead Time / Delivery Date: The amount of time required to fulfill a request, often expressed as "N business days." This tool translates that into an exact calendar date.
Custom Holidays: The ability to manually click and designate specific dates on the calendar (e.g., Year-end holidays from Dec 29 to Jan 3) to exclude them from the business day count.

faq,

FAQ

Q.Does this accurately reflect Japan's complex public holidays?: Yes. The engine uses strict Japanese holiday logic, accommodating vernal/autumnal equinox dynamics, multi-day substitute holidays, and Golden Week special rules.
Q.Is the starting day counted as Day 1?: By default, the tool operates on an "exclusive" basis where the day *after* the start date is Day 1 (a standard business practice). You can toggle this to "inclusive" via settings.
Q.How do I add my company's unique winter break to the calculation?: Simply use the interactive calendar view below the settings. Clicking on any date will toggle its status to a "Custom Holiday" and update your calculations instantly.
Q.Can I calculate for a 6-day workweek?: Yes. In the "Day of Week" settings panel, uncheck Saturday. The calculator will treat Saturdays as normal working days instead of days off.
Q.Is it possible to count backward (e.g., 5 business days ago)?: Currently, the tool supports forward projection (X days later) and duration counting (days between two dates). Retroactive calculation is planned for future updates.
Q.What is the difference between "Total Days" and "Business Days"?: Total Days means absolute calendar days (including weekends/holidays). Business Days count only your defined working output dates.
Q.Are calculations processed server-side?: No, all date math, logic parsing, and calendar rendering are executed instantly via your local browser. No inputs are tracked or analyzed.