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§ · free tool
Date Calculator. Calendar math, done right.
Days between dates, add or subtract durations, and exact age with a birthday countdown — true calendar arithmetic, computed entirely in your browser. Nothing is uploaded.
A free online tool by Digital Heroes
Operation
Defaults to today — change it to find the age on any date.
Calculated locally — nothing is sent anywhere.
Calendar math, done right
Months and years have different lengths, and leap years shift February — so “3 months from now” isn’t simply 90 days. This calculator uses true calendar arithmetic for adding, subtracting and measuring ages (clamping to the end of shorter months instead of rolling over), and can count working days for project planning. It all runs in your browser: fast, private and free forever.
§ 02 · what you can do
Every date question, answered instantly.
Days between datesThe gap between any two dates, broken into years, months and days — plus total days, weeks and hours.
Business-day countsOne toggle excludes weekends and counts Monday–Friday working days for project planning.
Add or subtract timeMove any date by years, months, weeks and days with calendar-correct month lengths and leap years.
Exact ageAge in years, months and days from a date of birth — on today’s date or any date you pick.
Birthday countdownDays until the next birthday and the age they’ll turn — Feb 29 birthdays handled sensibly.
Weekday & ISO dateSee which weekday a result lands on, its ISO date, and the net days from your start date.
§ 03 · how to use it
Four steps, no manual.
- Pick a tab: Difference to measure the gap between two dates, Add / Subtract to move a date forward or back, or Age for an exact age with a birthday countdown.
- Enter your dates — results update instantly as you type, no button to press.
- In the Difference tab, toggle business days to exclude weekends and count Mon–Fri working days only.
- Read the result: the headline number, the breakdown tiles, and a plain-English sentence explaining exactly what was calculated.
§ 04 · faq
Frequently asked questions.
Is the Date Calculator free?
Yes — completely free for everyone. No sign-up, no account and no usage limits.
Is it private? Are my dates uploaded anywhere?
No upload, ever. All calculations run entirely in your browser on your own device — the dates you enter never leave your computer, and once the page has loaded the math keeps working without a connection.
How are months and years counted when adding time?
With true calendar arithmetic, not fixed 30-day months. Years and months are applied first, clamping to the end of shorter months (Jan 31 + 1 month = Feb 28, or Feb 29 in a leap year), then weeks and days are added on top.
What counts as a business day?
Monday through Friday. Saturdays and Sundays are excluded automatically. Public holidays are not excluded — they vary by country, so treat the count as working weekdays.
How are February 29 birthdays handled?
In non-leap years the next-birthday countdown rolls a Feb 29 birthday to March 1, the first day after February 28 — the most common legal convention. In leap years it lands on Feb 29 itself.
Published · Last updated .
