Age & Date Calculator
Calculate exact age, the difference between two dates, or add and subtract days, weeks, months, and years. Free, instant, in your browser.
What is an age and date calculator?
It finds your exact age in years, months, and days, measures the gap between two calendar dates, or shifts a date forward and backward by years, months, weeks, and days.
Use it for birthdays, project timelines, contract deadlines, and quick “what date is 90 days from now?” checks. Results update as you change inputs - no sign-up and no data sent to a server.
Everyday examples
Exact age
Born 15 June 1990 – see years, months, days, total days lived, and next birthday.
Project deadline
From kick-off to launch – calendar difference plus optional business days (Mon–Fri).
Add 90 days
Start from today, add 3 months and 2 weeks to plan a follow-up or review date.
How to use this calculator
Pick a tab, enter dates, and read results instantly. All math runs locally in your browser – no account, no server upload.
When is this useful?
Birthdays and milestones
Check exact age in years, months, and days for forms, celebrations, or eligibility checks.
Projects and contracts
Measure time between start and end dates, including workdays for SLA or delivery windows.
Planning ahead
Add or subtract weeks and months from a base date to set reminders or deadlines.
Common mistakes
Dividing days by 365
Calendar age uses full years and months, not a simple day count divided by 365.
Ignoring leap years
29 February birthdays are handled; in non-leap years the next birthday falls on 28 February.
Expecting public holidays
Business days exclude weekends only – national holidays are not removed automatically.
Worked examples
Sample inputs and typical outputs. Your locale may format dates differently; the logic stays the same.
| Scenario | Input | Output | Real-world context |
|---|---|---|---|
| Exact age | Birth 1990-06-15, as of 2026-05-21 | 35 y, 11 m, 6 d | Forms asking for age on a specific date |
| Project span | From 2024-01-01 to 2024-06-30 | ~181 calendar days | Half-year roadmap or internship length |
| Business days | Same range, workdays only | Fewer than calendar days | SLA counted Mon–Fri, excluding weekends |
| Add duration | Base today + 90 days | Date ~3 months ahead | Follow-up appointment or warranty expiry |
| Leap birthday | Birth 2000-02-29, as of 2025-03-01 | 25 y (Feb 28 rule in non-leap years) | Legal age when born on 29 February |
Formulas
- Calendar age
Years, months, days from birth to “as of” date (calendar components) - Total days
End date − start date (midnight to midnight, date-only) - Business days
Count Mon–Fri between dates (weekends excluded) - Add / subtract
Shift base date by years, months, weeks, and days
Key date and age terms
Calendar age
Age expressed as whole years, months, and days – not just total days divided by 365.
Business day
Monday through Friday; Saturdays and Sundays are excluded in the workdays mode.
Leap year
A year with 29 February; affects day counts and birthdays on 29/02.
Date-only calculation
Times and time zones are ignored; only calendar dates are used.
Frequently Asked Questions
Age, date differences, and calendar math explained.
How is age calculated?
We use calendar years, months, and days between birth date and the "as of" date, not just dividing total days by 365.
What about 29 February birthdays?
In non-leap years the next birthday is treated as 28 February for counting purposes.
Are business days Mon–Fri only?
Yes. The workdays option excludes Saturdays and Sundays; public holidays are not excluded.
Is this legal or medical advice?
No. It is a general date tool for planning. Confirm deadlines with official sources when required.
About these results
Outputs follow the formulas on this page from the dates you enter. Time zones and daylight saving are not applied – use date-only values.