# Age Calculator Tool

> Free, private browser-based calculators and transparent guides for chronological age, age differences, and Gregorian calendar date intervals.

## Calculators

- [Chronological Age Calculator](https://agecalculatortool.org/): Calculates age from a date of birth to any reference date in complete years, months, days, total days, and weeks.
- [Age Difference Calculator](https://agecalculatortool.org/age-difference-calculator/): Compares two birth dates, identifies the older person, and reports the exact calendar gap.

## Method and Trust

- [Calculation Method](https://agecalculatortool.org/calculation-method/): Documents the calendar-anchor algorithm, Gregorian leap-year rule, month-end clamping convention, date limits, and reference test cases.
- [About Age Calculator Tool](https://agecalculatortool.org/about/): Explains the editorial approach, testing process, privacy model, and limits of the tools.
- [Privacy Policy](https://agecalculatortool.org/privacy-policy/): Describes local browser processing, hosting logs, cookies, storage, and external services.
- [Terms of Use](https://agecalculatortool.org/terms/): Defines informational use, user responsibilities, and limits of calculator results.

## Core Guides

- [What Is Chronological Age?](https://agecalculatortool.org/blog/what-is-chronological-age/): Defines chronological age and distinguishes it from biological, developmental, mental, and corrected age.
- [How to Calculate Chronological Age](https://agecalculatortool.org/blog/how-to-calculate-chronological-age/): Gives a step-by-step calendar-anchor method with ordinary and month-end examples.
- [Age on a Specific Date](https://agecalculatortool.org/blog/how-to-calculate-age-on-a-specific-date/): Shows how to choose and use a past, present, or future reference date.
- [Chronological Age in Years, Months, and Days](https://agecalculatortool.org/blog/chronological-age-years-months-days/): Explains each unit in a detailed age result and how it differs from total days.
- [Chronological Age vs Decimal Age](https://agecalculatortool.org/blog/chronological-age-vs-decimal-age/): Compares calendar-based and continuous numeric age formats.

## Applied and Accuracy Guides

- [School Enrollment Cutoff Dates](https://agecalculatortool.org/blog/chronological-age-school-cutoff-dates/): Calculates a child's age on a published cutoff while separating arithmetic from eligibility policy.
- [Leap-Day and Month-End Calculations](https://agecalculatortool.org/blog/leap-day-and-month-end-age-calculations/): Explains February 29 and missing-day conventions with worked examples.
- [Common Age Calculation Mistakes](https://agecalculatortool.org/blog/common-age-calculation-mistakes/): Identifies seven frequent errors involving years, reference dates, fixed month lengths, and edge cases.
- [Verify an Age Calculator Result](https://agecalculatortool.org/blog/how-to-verify-age-calculator-result/): Provides a reproducible checklist using calendar anchors, boundary tests, and total days.
- [Calculate the Age Difference Between Two People](https://agecalculatortool.org/blog/how-to-calculate-age-difference/): Explains direct birth-date comparison and why rounded current ages should not be subtracted.
- [All Age Calculation Guides](https://agecalculatortool.org/blog/): Lists every published guide with its topic and publication date.

## Key Facts

- Both calculators run in the visitor's browser; entered dates are not submitted to an application server.
- Supported dates run from January 1, 1900 through December 31, 2100.
- Detailed results count complete calendar years, complete calendar months, and remaining days in that order.
- Total days are calculated separately with date-only Gregorian arithmetic.
- A missing target day is clamped to the final valid day of the target month.
- Under the site's stated convention, a February 29 anniversary falls on February 28 in a non-leap year.
- Calculator results provide calendar information and do not determine legal, medical, educational, or assessment outcomes.

## Contact and Feeds

- [Contact and Issue Reporting](https://agecalculatortool.org/contact/): Explains what to include when reporting a calculation or content issue and what personal data to omit.
- [RSS Feed](https://agecalculatortool.org/rss.xml): Machine-readable feed of all published guides.
- Website: https://agecalculatortool.org/