Age Calculator
NewCalculate exact age in years, months, and days from a date of birth, plus total days lived and days until your next birthday.
Frequently Asked Questions
How does the years/months/days breakdown avoid off-by-one errors around month-end dates?
It borrows days from the previous calendar month (using that month's actual length, e.g. 28, 30, or 31 days) whenever the day-of-month component goes negative, and borrows a year when the month component goes negative — the same approach a calendar app uses internally, rather than a fixed 30-day-month approximation.
What does "as of date" let me do?
It defaults to today, but you can set it to any date to calculate how old someone was (or will be) on a specific date — useful for eligibility checks, contracts, or historical records.
How is "days to next birthday" calculated across a year boundary?
It builds the birthday date in the current "as of" year; if that date has already passed this year, it recalculates using next year's birthday instead, so the count is always the true number of days forward, never negative.
Does this account for leap years?
Yes — all the date math uses native JavaScript Date objects, which correctly handle leap years (including February 29th) when computing total days and borrowed month lengths.
Is my date of birth sent anywhere?
No — all calculations run in your browser using JavaScript Date arithmetic. Nothing is transmitted or stored.