This date calculator answers four common questions in one place: how many days are between two dates, what date results from adding or subtracting days, weeks, months or years to a date, how many business days fall within a period, and someone's exact age in years, months and days.
It's built for work, school and paperwork: invoice deadlines, delivery dates, contract due dates or forms that ask for an exact age. The business-day weekend is configurable, so it also works for countries where the work week doesn't run Saturday–Sunday.
How to use
- 1Pick a mode: difference between dates, add or subtract days, business days, or exact age.
- 2Select the dates with the date picker or type them directly.
- 3In business days, choose which days count as the weekend and add any custom holidays you need.
- 4Read the result, then copy it or download it as a TXT file to keep it.
What you can do
- Difference between dates in days, months and years
- Add or subtract days from a date
- Business days and exact age
What each mode calculates
Each mode answers a different date question, with the same care for edge cases: leap years, months of different lengths, and dates entered in reverse order.
- Difference: the exact number of days between two dates, plus its equivalent in weeks, months and years.
- Add/subtract: what date results from adding or removing days, weeks, months or years from a base date.
- Business days: how many working days fall between two dates, excluding the weekend (configurable) and any holidays you list.
- Exact age: years, months and days lived, plus how many days remain until the next birthday.
Business days with a configurable weekend
Most business-day calculators assume the weekend is always Saturday and Sunday, but that's not universal — several countries observe a Friday–Saturday weekend instead. This calculator lets you choose which weekdays don't count as working days, on top of excluding specific holidays.
- Saturday–Sunday weekend: the most common pattern in Europe and the Americas.
- Friday–Saturday weekend: used in several countries in the Middle East.
- You can add your own holidays (one per line or comma-separated) for your country, your company or a specific academic calendar.
Good practice when working with deadlines
When a deadline really matters — a contract, a payment, a legal filing — it's worth distinguishing between calendar days and business days, since the result can change quite a bit, and checking whether the start or end date should count toward the total.
- A "30-day" term in a contract usually means calendar days unless it explicitly says "business days."
- When calculating a deadline, confirm whether today counts as day one of the period or not.
- For recurring due dates (monthly payments, subscriptions), the “Add/subtract” mode with the “Months” unit automatically respects end-of-month rollovers.
Frequently asked questions
How do I calculate the number of days between two dates?
Subtract the start date from the end date and count the full days of difference. The calculator also shows the count including both dates (useful for knowing how many days a period "spans") and its equivalent in years, months and days.
How are business days between two dates calculated?
Every day in the period is counted, then weekend days (Saturday and Sunday, or whatever pattern you choose) and any holidays you've listed are excluded. The “Business days” mode does this automatically.
Can I add or subtract months without breaking the date?
Yes. If the resulting day doesn't exist in the target month — for example, adding a month to January 31 — the calculator rolls back to the last day of that month (February 28 or 29) instead of producing an invalid date.
How is someone's exact age calculated?
It compares the birth date and the reference date and works out the complete years, months and days between them, along with the total number of days lived and the date of the next birthday.
Is the weekend always Saturday and Sunday?
Not necessarily — several countries observe Friday and Saturday as the weekend instead. That's why the “Business days” mode lets you choose which weekdays are excluded from the count.
Can I save or export the result?
Yes. Every mode has a button to copy a summary of the result and another to download it as a text (.txt) file.