How it works
- 1Choose Age or Calendar Days mode.
- 2Enter the relevant date or dates.
- 3Calculate exact age, day difference, or a date shifted by a chosen number of calendar days.
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BROWSER · Calendar Date / JavaScript
I need to calculate Age & Calendar Day
Age & Calendar Day Calculator
Calculate exact age in years, months and days, count calendar days between two dates, or add and subtract days from any date.
✓ Runs locally in your browser✓ Calendar-aware date arithmetic✓ No account required
About this tool
Age & Calendar Day Calculator performs calendar-aware date arithmetic locally in your browser: exact age, elapsed and inclusive calendar-day counts, and date addition or subtraction.
Common uses
age calculatorcalculate my agehow old am iage from date of birth
TOOL GUIDE
Age & Calendar Day Calculator: practical guide
Calculate exact age in years, months and days, count calendar days between two dates, or add and subtract days from any date.
The workflow is designed for browser-based use, so you can complete the task without installing a desktop application.
When is this useful?
- Calculating an exact age in years, months, and days
- Counting elapsed or inclusive calendar days between dates
- Adding or subtracting calendar days from a date
- Checking date arithmetic across leap years and different month lengths
How to use it
- Choose Age or Calendar Days mode.
- Enter the required date or dates.
- Choose elapsed/inclusive counting or a day offset where relevant.
- Calculate and review the result.
Good to know
Yes. Age is calculated with calendar-aware year, month and day arithmetic rather than assuming a fixed number of days per month or year.
Frequently asked questions
What is the difference between elapsed days and inclusive calendar days?
Elapsed days is the number of 24-hour calendar boundaries between the dates. Inclusive calendar days counts both the start and end dates; for example, August 1 through August 2 is 1 elapsed day but 2 inclusive calendar days.
Does the age calculator account for leap years and different month lengths?
Yes. Age is calculated with calendar-aware year, month and day arithmetic rather than assuming a fixed number of days per month or year.
Can I add or subtract calendar days from a date?
Yes. Calendar Days mode can move a date forward or backward by an exact integer number of calendar days.