Use the day before the common-year birthday
Input and settings
Birth: 2000-02-29 / Reference: 2023-02-27
Expected result
22 years old / 1 day until the next birthday Parts: 22 years, 11 months, 29 days / Date difference: 8,399 days
Age Calculator
Enter a date of birth to calculate age today or on another date, including the next birthday and the total days between the dates.
How to use
- Enter the date of birth.
- Choose the reference date.
- Review the age and elapsed period at that reference date.
Enter dates
Change the reference date to check your age on any past or future date.
Age
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Next birthday
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Total days
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Read each age result correctly
The main result is your age in completed years on the reference date. The calendar breakdown shows the remaining months and days, while total days measures the full elapsed date range.
The next-birthday result uses the same reference date, so you can check a past or future date without changing your date of birth.
About this tool
Calculate your age from a date of birth and a reference date. Along with your age in completed years, you can see the calendar time in years, months, and days and how long remains until the next birthday.
All calculations happen in your browser. Your date of birth and reference date are not saved or sent to a server.
A future reference date gives the age on that date
Set the birth date to 2000-02-29 and the reference date to 2028-02-29. The result is exactly 28 years. The reference date can be a planned future date, not only today.
- For non-leap years, a February 29 birthday is treated as February 28 in birthday calculations. This does not establish a legal or administrative age rule.
- Total days means the interval between the two selected dates. With a future reference date, it is not a claim about days already lived.
Try a use case and check the result
Compare the day before and the birthday in a common year for a fixed leap-day birth. Reference dates are not the real current date.
Example buttons replace the inputs and settings above and calculate. Restore previous input steps back one example at a time. After trying multiple examples, repeat restore to return to your original input. This history is lost when the page closes.
Check this tool’s common-year birthday rule
Input and settings
Birth: 2000-02-29 / Reference: 2023-02-28
Expected result
23 years old / The reference date is the birthday Parts: 23 years, 0 months, 0 days / Date difference: 8,400 days
How to read the result
This implementation treats 28 February as a leap-day birthday in common years. Today is the birthday refers to the selected reference date. Do not confuse the fixed 2023-02-28 reference with the current date. Year/month/day parts adjust calendar month ends and use different units from the total date difference.
Scope and limits
The form accepts years 1–9998 with birth on or before the reference date. Birth time, time-zone offsets and institution-specific age rules are not modeled. The initial reference is the device’s local date when the page opens; the age tool’s Today button reads the local date at the time you click it. Entered dates and example history are lost when the page closes.
Verification: existing calculateAgeYears, calculateAgeParts and daysBetweenDates checks cover full years, month-end adjustment and total days. Browser checks cover the next leap-year birthday, rejection of a reference before birth, device time zones and midnight boundaries.
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Frequently asked questions
How is age calculated?
Your age is calculated from your date of birth to the reference date, using the number of whole years that have passed.
Can I calculate age on a past or future date?
Yes. Change the reference date to calculate the age on that date.
How are February 29 birthdays handled?
February 29 is used in leap years. For this general calendar calculation, February 28 is treated as the corresponding birthday in other years. This tool does not provide a legal determination of age.
Is my date of birth saved?
No. The dates you enter are not saved, and the calculation takes place in your browser.
Can I see the days until the next birthday?
Yes. The result shows both the remaining days and the date of the next birthday.
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Inputs and storage
Keep any content you need before clearing. This tool does not autosave inputs or results. Reloading or closing the page, clearing inputs or resetting may discard your work.
Favorites and language preferences are stored separately and may be lost when site data is cleared. Tool resets and site-data deletion do not delete files already downloaded to your device.