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Calculate your exact age in years, months and days — plus total weeks, days, hours, minutes and seconds.
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Date Calculator
Find the difference between two dates, or add and subtract days, weeks, months and years — calendar-accurate.
Runs entirely in your browser — nothing you type is uploaded.
How to use the Date Calculator
- Choose a mode: Difference (the gap between two dates) or Add / Subtract (move a date forwards or backwards).
- For a difference, enter a start date and an end date. Tick “include the end date” if you want to count both endpoints.
- To add or subtract, enter a starting date, choose Add or Subtract, then an amount and a unit (days, weeks, months or years).
- Press Calculate (or the Enter key), then Copy result or Reset.
What the Date Calculator does
The Date Calculator answers two everyday questions. First, how far apart are two dates? It shows the gap in total days, in weeks and days, and as calendar-accurate years, months and days. Second, what date is a certain time before or after another date? It moves a date forwards or backwards by a number of days, weeks, months or years and gives you the exact result.
Difference vs adding and subtracting
The two modes are different jobs. Difference takes two dates you already know and measures the distance between them. Add / Subtract takes one date and a length of time, and works out a new date. Use the first to count down to an event or measure a duration; use the second to find a deadline, a due date or an anniversary.
Examples
- Days between
1 Jan 2026 → 31 Jan 2026 = 30 days(or 31 if you include the end date). - Add days
1 Jan 2026 + 90 days = 1 Apr 2026. - Add a month (clamped)
31 Jan 2026 + 1 month = 28 Feb 2026. - Leap year
31 Jan 2024 + 1 month = 29 Feb 2024. - Subtract a year
29 Feb 2024 + 1 year = 28 Feb 2025.
Leap years and month-end handling
Dates are not just numbers — months have different lengths and leap years add a day. This calculator is calendar-aware: it counts real days between dates, and when you add or subtract months or years it clamps to the last valid day of the target month rather than “rolling over” into the next month. That is why 31 January plus one month lands on 28 February (or 29 February in a leap year) instead of 3 March. All maths uses date-only values, so time zones and daylight-saving changes never shift your result.
Benefits and use cases
- Deadlines & due dates — add days or weeks to find when something is due.
- Countdowns — see how many days, weeks or months until an event.
- Anniversaries & milestones — measure how long since a date, or project a future one.
- Planning — work backwards from a target date to find a start date.
Is it private?
Yes. The Date Calculator runs entirely in your web browser using JavaScript. The dates you enter are never sent to a server, never stored, and never shared. There is no sign-up and no tracking.
Frequently Asked Questions
Is the Date Calculator free?
Yes. It is completely free to use, with no account, sign-up or limits.
How does it count the days between two dates?
By default it counts the number of full days from the start date up to (but not including) the end date, so 1 January to 31 January is 30 days. Tick “include the end date” to count both endpoints, which gives 31 days.
Does it handle leap years and month lengths correctly?
Yes. All calculations are calendar-aware and use each month’s real length and leap years. Adding months or years clamps to the last valid day — for example, 31 January plus one month becomes 28 February (or 29 February in a leap year).
What happens if I enter the end date before the start date?
The difference is shown as an absolute value, so the order of the two dates does not change the number of days, weeks or months — it always shows the gap between them.
Is my data stored or sent anywhere?
No. All calculations run locally in your browser — the dates you enter are never uploaded, saved or shared.