Age & Birthday Calculator
Find completed years, total elapsed days and days until the next birthday. Choose the anniversary rule for February 29 birthdays.
1. Set up your options
The reference date can be today or any date after birth. For leap-day birthdays, choose which anniversary convention to use. This does not determine legal age.
2. Review & export
Ready. Try the example to see how it works.
Using Age & Birthday Calculator
Find completed years, total elapsed days and days until the next birthday. Choose the anniversary rule for February 29 birthdays.
- Start with the working example to explore the workflow, or add your own inputs.
- Choose the options, build a preview and review the result table and notes.
- Copy or download the output. When inputs change, build a fresh preview before exporting.
Example
The reference date can be today or any date after birth. For leap-day birthdays, choose which anniversary convention to use. This does not determine legal age.
Questions & answers
Can I calculate age on a future date?
Yes. Set the reference date to the date you want to check.
What does completed years mean?
It counts anniversaries reached by the reference date using your selected leap-day convention.
How are February 29 birthdays handled?
In a non-leap year, you can use February 28 or March 1 as the anniversary.
Why is days until birthday zero?
The reference date is the anniversary itself. The calculator includes that day rather than jumping to next year.
Is the Today button based on my timezone?
Yes. It uses the calendar date reported by your browser’s local clock.
Can I save the result?
Yes. Download the text result or JSON report, or copy the result. Editing inputs invalidates the previous result until you calculate again.
Is my input uploaded for processing?
Processing runs in a local browser worker with no input upload and no account. Website advertising and analytics are described in the privacy information.
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