Calculate Date Calculator
Days between dates, dates shifted by any amount, and business-day counts that skip weekends — three date tools in one, with the weekday always shown.
How it works
All math is done on calendar days (in UTC, so daylight-saving changes can never shift a result). Days between is the exact difference between the two dates, also broken into years, months and days. Add/subtract moves a date by days or weeks exactly, and by months or years on the calendar — adding a month to Jan 31 lands on Feb 28 rather than overflowing into March. Business days counts Mondays to Fridays only; the count starts the day after your start date, and the end date is included only if you tick the box.
Formula & worked example
Formula: Days between = end date − start date counted in whole days, leap days included. The same span is also broken into years, months and days by calendar borrowing and into weeks; the tool can instead add or subtract days, weeks, months, years or business days to or from any date.
Worked example: From 1 March 2026 to 15 June 2026 is 106 days — that is 3 months and 14 days, or 15 weeks and 1 day.
When to use this
- A contract, notice period or deadline is '90 days from signing' and the date matters.
- You are counting business days for shipping, processing or a statutory window.
- Two dates need their exact gap — days, weeks and months — for planning.
- A project plan needs dates added or subtracted in weeks and months, not guesses.
How to use it, step by step
- Pick the mode: days between, add/subtract, or business days.
- Enter the start date (and end date, for gaps).
- For add/subtract, set the amount and unit — days, weeks, months or years.
- Read the resulting date and its day of the week.
- For deadlines, sanity-check whether the landing day falls on a weekend.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Start / end dates | The span being measured | Inclusive/exclusive conventions differ — see the FAQ |
| Amount + unit | What to add or subtract | Days, weeks, months, years |
| Business days | Weekdays excluding weekends | Public holidays are not built in |
Another worked example
Thirty days from 6 November 2026 lands on 6 December 2026 — a Sunday, which quietly pushes any 'business day' deadline to Monday the 7th. Between 2 November and 13 November 2026 there are 10 business days, not 12 calendar days: the two-day gap is where most deadline math goes wrong.
Frequently asked questions
How many business days are in a year?
A typical year has about 260–262 weekdays. 2026 has 261 business days before holidays — the exact count for any span is in the Business days mode above.
Does "days between" count both endpoints?
No — it is the difference, so Jan 1 to Jan 2 is 1 day. If you need an inclusive count (both the first and last day), add 1. The business-days mode has an explicit checkbox for its end date.
What date is 90 days from today?
Use the Add / subtract mode: enter today’s date, choose Add, 90, Days. It shows the resulting date and its weekday — handy for deadlines, trials and payment terms like "net 90".
Why does adding a month to Jan 31 give Feb 28?
Calendar months have different lengths. Adding one month keeps the same day-of-month when it exists and clamps to the month’s last day when it does not — the convention calendars and contracts use.
🎂 How old are you, exactly?
The Age Calculator turns two dates into your exact age, total days lived and a next-birthday countdown.
Are the start and end days counted?
The difference counts whole days between the dates (end minus start), the standard convention: Monday to Tuesday is 1 day. Legal deadlines sometimes count inclusively or exclude the trigger day — if the stakes are legal, confirm the convention for your document.
Are public holidays excluded from business days?
No — holidays vary by country and state, so business days here means Monday–Friday. Subtract your local holidays from the result for a statutory count.