Date Calculator (Add or Subtract Days)
Instantly get the date and weekday N days or N business days after or before any date. Weekends and holidays can be skipped too.
1. Enter a date and a number of days
Enter the start date and how many days after (or before) it.
Unit
After or before
Includes the start date, as in “day 7 counting from today”.
2. Results
The date and weekday appear as you type.
- Date
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- Date (YYYY-MM-DD)
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- Days from the start date
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Everything is calculated on this device. The numbers you enter are never sent anywhere.
Holidays are calculated from the rules of Japan’s holiday law. The Vernal and Autumnal Equinox Days are only made official in February of the year before, so dates further ahead are predictions.
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How to use
1. Enter the start date and number of days
“Start date” starts as today. To use another day, tap the field and pick a date. Then type a number in “Number of days”, or tap one of the buttons below it, such as “10”. The date and weekday appear right away in “Results” below.
“Start date” on the left starts as today. To use another day, click the field and pick a date. Then type a number in “Number of days”, or click one of the buttons below it, such as “10”. The date and weekday appear right away in “Results” on the right.
2. Choose after or before
Tap “10 days before” to recalculate a date before the start date. Choose “Weeks”, “Months” or “Years” under “Unit” to get a date N weeks, months or years away.
Click “10 days before” to recalculate a date before the start date. Choose “Weeks”, “Months” or “Years” under “Unit” to get a date N weeks, months or years away.
3. Count business days
Under “Unit”, tap “Business days” to recount, skipping Saturdays and Sundays. “Days off skipped” in the results below shows how many days off were skipped. To also skip Japanese public holidays, turn on “Also skip Japanese holidays”, and add other days off, such as your country’s holidays or company closures, in “Other days off”.
Under “Unit”, click “Business days” to recount, skipping Saturdays and Sundays. “Days off skipped” in the results on the right shows how many days off were skipped. To also skip Japanese public holidays, turn on “Also skip Japanese holidays”, and add other days off, such as your country’s holidays or company closures, in “Other days off”.
4. Copy the results
Tap the copy button to the right of “Date” to copy it in a form like “Fri, May 8, 2026”. “Copy all results” copies the date and the day counts together.
Click the copy button to the right of “Date” to copy it in a form like “Fri, May 8, 2026”. “Copy all results” copies the date and the day counts together.
Great for
Working out payment or filing deadlines
See right away which date and weekday a deadline like “net 30” or “within 10 business days of receipt” falls on.
Accounting and admin staff
Telling customers when an order ships or arrives
Get the date “3 business days” from now, skipping weekends and holidays, and use it straight in your message to customers.
Shop and online store owners
Finding the date of an anniversary or event
Look up the date and weekday of a baby’s 100th day, or one year since you started dating.
Anyone celebrating family and loved ones
Counting back from a deadline
Choose “Before” to see when you need to start: 2 weeks or 5 business days before the deadline.
Planners and students
Good to know before you start
- Only Japanese public holidays are built in. For other countries’ holidays, enter them in “Other days off”.
- Saturdays and Sundays are always counted as days off. If your business has other closures, such as a summer shutdown, add them in “Other days off”.
- Legal and contract deadlines may have their own rules for when the last day falls on a day off. For important deadlines, check the other party’s rules too.
How the days are counted
“10 days later” is the day you reach after counting 10 days, with the day after the start date as day 1 (the start date itself isn’t counted). This is how legal time periods are usually counted too. To make the start date day 1, as in “day 7 counting from today”, turn on “Count the start date as day 1”.
“1 month later” is the same day in the next month. If that month has no such day, as with 1 month after January 31, the last day of the month is used (February 28, or 29 in a leap year). Business days skip weekends and the days off you choose (Japanese holidays, the New Year break and other days off).
FAQ
Answers to the things people most often wonder about when calculating dates.
Are the dates I enter sent anywhere?
No. All calculations happen in the browser on your device, and the dates and days off you enter are never sent to a server. Even the holidays are calculated on your device rather than fetched from elsewhere.
Is the start date counted as day 1?
Not by default. The day after the start date is day 1 (10 days after October 1 is October 11). Turn on “Count the start date as day 1” to make the start date day 1 (day 10 counting from October 1 is October 10).
How are business days counted?
Saturdays, Sundays and the days off you turned on (Japanese holidays, the New Year break and other days off) are skipped, and the remaining days are counted one by one. Even if the start date is a day off, counting starts from the next business day.
Which years do the holidays cover?
1980 to 2099, calculated from the rules of Japan’s holiday law. Substitute holidays, citizens’ holidays, the 2019 enthronement holiday and the holidays moved for the 2020 and 2021 Olympics are all included. The Vernal and Autumnal Equinox Days are only made official in February of the year before, so dates further ahead are predictions.
Can I skip company holidays or my own country’s holidays?
Yes. Choose “Business days” and enter the dates in “Other days off”, one per line. What you enter is kept on this device, so it’s still there the next time you open the tool.
What is 1 month after January 31?
February 28 (February 29 in a leap year). When the next month has no such day, the last day of that month is used. It works the same way as EDATE in spreadsheets.
Can I calculate N weeks or N years from a date?
Yes. Choose “Weeks”, “Months” or “Years” under “Unit”. Weeks move 7 days at a time; months and years move by calendar months and years. To count business days, choose “Business days” under “Unit”.
Can I count back from a deadline?
Yes. Enter the deadline as the start date and choose the “before” button (such as “10 days before”). This works with business days too.
Can it show the number of days between two dates?
This tool works out a date from a date and a number of days. “Days from the start date” in the results also shows the number of calendar days.
Is it free?
Yes. No sign-up, and no ads.
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