How do I calculate exact age considering leap years?

The calculator correctly handles leap years by subtracting the birthdate from today's date and normalizing months/days when the difference is negative. The algorithm is equivalent to `differenceInYears` / `differenceInMonths` of dates-fns, considering February 29th as a valid day.

Difference between UTC and local time in date calculations?

UTC is the absolute reference time (Zulu time), local time applies browser timezone offset. The calculator uses `new Date()` in local time for user perception consistency; for cross-timezone calculations, it's recommended to normalize all dates to UTC first.

Which JavaScript library for date math: date-fns vs luxon vs dayjs

Date-fns is modular and tree-shakable (~5 KB gzipped per function). Luxon supports better timezone and native i18n (~70 KB). dayjs is the lightest (~7 KB). For pure date math, date-fns is the optimal compromise; for complex timezones, Luxon.

Can I integrate this calculation into a REST API?

Yes: the algorithm is stateless and can be ported to Java (java.time.Period.between), Python (relativedelta) or Spring Boot as a service method. Input: ISO-8601 dates (YYYY-MM-DD), output: object

How do I handle February 29th when it's not a leap year?

In Java `LocalDate.of(2025, 2, 29)` throws DateTimeException; JavaScript `new Date(2025, 1, 29)` performs rollover to March 1st. The calculator predicts the next birthday on February 28th in non-leap years, consistent with ISO 8601 behavior.

Is browser-level millisecond precision reliable?

Performance.now() offers sub-millisecond precision; Date.now() is limited to 1 ms. In Chrome/Firefox resolution is reduced to 5 μs to mitigate timing attacks (Spectre). Sufficient for age calculations, not for high-resolution benchmarks.

Age Calculator | Federico Calò

Insert birthdate

Select your birthdate to calculate your exact age and all related statistics.

Date of birth

Select your birthdate to calculate your age.

Come utilizzare Calcolatore Età

Inserisci la data di nascita

Seleziona la tua data di nascita tramite il selettore di date. Il calcolatore accetta qualsiasi data dal 1900 ad oggi.

Visualizza l'età esatta

Il calcolatore mostra immediatamente anni, mesi e giorni esatti trascorsi dalla nascita, usando la data odierna come riferimento.

Scopri statistiche dettagliate

Nella griglia dei risultati trovi il totale di giorni, settimane e mesi vissuti, insieme al giorno della settimana in cui sei nato e al tuo segno zodiacale occidentale.

Controlla il prossimo compleanno

La sezione dedicata mostra la data esatta del prossimo compleanno e quanti giorni mancano, così non ti dimentichi di festeggiare.

Suggerimenti

Il calcolo dell'età usa la data locale del tuo browser, quindi è preciso per il tuo fuso orario.
Il segno zodiacale mostrato è quello occidentale (tropicale). Esiste anche lo zodiaco cinese, che segue un sistema diverso basato sull'anno lunare.
Il contatore del prossimo compleanno si aggiorna automaticamente ogni volta che cambi la data di nascita.

Domande frequenti

How is exact age calculated?

Age is calculated by subtracting the birthdate from today's date. Years, months, and days are calculated with attention to months with varying numbers of days (28, 29, 30 or 31), ensuring always a precise result.

How is the zodiac sign determined?

Western zodiac sign is based on birth date (month and day). Each sign covers a fixed range of dates: for example, Aries spans from March 21 to April 19. Capricorn has an interval that crosses the year change (December 22 – January 19).

What happens if I was born on February 29?

If born on February 29, the calculator handles leap years correctly: your next birthday will be calculated on either February 28 or March 1 depending on system implementation. The total day count remains accurate.

Does the calculator work for past dates?

Yes, the calculator works for any past date up to January 1, 1900. It's also useful for calculating the age of historical people or for curiosity about ancient dates.

How are total months of life counted?

Total months are calculated as: complete years x 12 + additional months. This is an approximate estimate based on whole months, not exact days per month.

Calculator Age