Date Add & Subtract Calculator
Add or subtract years, months, weeks and days from a date, with clear end-of-month handling, or move forward or back by business days with your own weekend days and holidays. Shows the result and every step.
Loading Date Add & Subtract Calculator…
About the Date Add & Subtract Calculator
Date Add & Subtract Calculator finds the date that is a given amount of time before or after a start date. In calendar mode you can combine years, months, weeks and days in one calculation; the result shows the new date, its day of the week, the total number of calendar days between the two dates and a step-by-step explanation. Years and months are applied first using calendar rules, so 31 January plus one month becomes the last day of February (28th, or 29th in a leap year), and the tool tells you when such an end-of-month adjustment happens.
Business-day mode moves forward or back by working days only, using the same weekend options as Toolsfy’s Business Days Calculator — Saturday and Sunday, Friday and Saturday, Sunday only, or your own custom weekdays — and skips any holiday dates you add yourself. No public-holiday calendar is used or implied. Dates are handled as whole calendar days in the Gregorian calendar, so time zones and daylight saving do not affect the result.
How to use
- Choose calendar mode or business-day mode.
- Pick the start date and whether to add or subtract.
- Enter years, months, weeks and days — or the number of business days, weekend days and any holidays.
- Click Calculate to see the result date, day of week and the steps used.
- Copy or download the summary.
Key features
- Years, months, weeks and days in one calculation, added or subtracted.
- Clear end-of-month handling with an explanation when a day is adjusted.
- Result date, day of week and total calendar-day difference.
- Business-day mode with Saturday–Sunday, Friday–Saturday, Sunday-only or custom weekends.
- Holidays you enter are skipped; nothing is assumed about public holidays.
- Leap years, month boundaries and negative values handled; Copy and Download Summary.
Best practices
- Check the end-of-month note when adding months to the 29th, 30th or 31st.
- Add months and days in separate steps if your contract or rule specifies a particular order.
- Enter all relevant holidays for business-day deadlines — public holidays vary by country and region.
- Confirm whether your deadline counts the start day; this tool starts counting from the next day.
- Keep a copy of the summary for records of how a deadline was calculated.
Benefits
- Quick, reliable date arithmetic without counting on a calendar.
- Transparent steps, including month-end adjustments.
- Working-day deadlines with your own weekends and holidays.
- Private: everything runs in your browser.
Frequently asked questions
What happens when I add a month to 31 January?
February has no 31st, so the last day of February is used: 28 February, or 29 February in a leap year. The result explains when this end-of-month adjustment happens.
In which order are years, months, weeks and days applied?
Years and months are applied first (as a total number of months), then weeks and days are added as exact calendar days. This matches the way most people count “1 month and 10 days”.
Can I use negative numbers?
Yes. A negative number moves in the opposite direction, so adding −3 days is the same as subtracting 3 days. You can also choose Subtract as the direction.
How does business-day mode count?
It starts from the day after the start date (or the day before when subtracting) and counts only days that are not weekend days or holidays you added. Adding 1 business day on a Friday with a Saturday–Sunday weekend gives Monday.
Are public holidays included?
No. Only holiday dates you add yourself are skipped. Public holidays differ by country and region, so add the ones that apply to you.
Do time zones or daylight saving affect the result?
No. Dates are counted as whole calendar days in the Gregorian calendar, so clock changes and time zones do not shift the result.