Can I calculate age for a future date?

Yes. Set the 'As of' date to any future day to see the age you will be on that date.

How are leap years and February 29 birthdays handled?

We follow Gregorian rules. For individuals born on February 29, the next birthday in non-leap years is observed on February 28 or March 1 depending on local legal tradition; this tool uses March 1 by default for date arithmetic and clearly documents the approach.

Why do totals sometimes differ by a day from other tools?

Some tools use local midnight with daylight-saving adjustments. This calculator normalizes to UTC to prevent DST-related off-by-one discrepancies.

Do you store my dates or personal data?

No. All calculations happen in your browser. No dates are transmitted or stored on a server.

Can I share a link with pre-filled values?

Yes. The tool supports URL parameters ?dob=YYYY-MM-DD&asof=YYYY-MM-DD&time=1 to prefill fields.

Age Calculator | Everyday Life Time & Date Tool

Q: How accurate is this age calculator?

It uses Gregorian calendar rules and UTC-based computations to avoid daylight-saving issues. If you include time of day, results are accurate down to the second.

Use this authoritative age calculator to compute the exact time between your date of birth and any “as of” date. Designed for everyday use and professional contexts, it returns your age in years, months, and days—plus totals in weeks, days, hours, minutes, and seconds.

Interactive Calculator

Date of birth *

As of date (comparison) *

Include time of day (hours/minutes/seconds precision)

Time of birth

As of time

Results

Chronological age —

Total months —

Total weeks —

Total days —

Total hours —

Total minutes —

Total seconds —

Next birthday —

Days until next birthday —

Weekday of next birthday —

Authoritative Content Ecosystem

Data Source and Methodology

Authoritative source: Dershowitz, N., and Reingold, E. M. “Calendrical Calculations.” 3rd ed., Cambridge University Press, 2008. Publisher page. All computations follow Gregorian calendar arithmetic and ISO 8601 representations for dates and times (ISO 8601:2019, ISO).

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

Given birth date B = (Y_b, M_b, D_b) and reference date R = (Y_r, M_r, D_r) in the proleptic Gregorian calendar:

Years component

$$ y \;=\; Y_r - Y_b - \begin{cases} 1, & \text{if } (M_r, D_r) \lt (M_b, D_b) \\ 0, & \text{otherwise} \end{cases} $$

Months component (after subtracting y years)

$$ m \;=\; \left(M_r - M_b - \mathbf{1}[D_r < D_b] \right) \bmod 12 $$

Days component (remaining days after adding y years and m months to B)

$$ d \;=\; \mathrm{daysBetween}\!\left(\mathrm{addMonths}(\mathrm{addYears}(B,y), m),\; R\right) $$

Totals in units use UTC-based epoch differences to avoid DST ambiguities:

$$ \Delta t = R_{\mathrm{UTC}} - B_{\mathrm{UTC}},\quad \text{days} = \left\lfloor \frac{\Delta t}{86400} \right\rfloor,\; \text{hours} = \left\lfloor \frac{\Delta t}{3600} \right\rfloor,\; \text{minutes} = \left\lfloor \frac{\Delta t}{60} \right\rfloor,\; \text{seconds} = \left\lfloor \Delta t \right\rfloor. $$

Glossary of Variables

Date of birth (B): Your birth date; required input.
As of date (R): The comparison date; required input (defaults to today).
Include time of day: Optional toggle to include hours, minutes, and seconds.
Chronological age (y, m, d): Years, months, and days since B to R.
Total months/weeks/days/hours/minutes/seconds: Aggregated elapsed time from B to R in the specified unit.
Next birthday: The next occurrence of your birth month and day relative to R.
Days until next birthday: Whole days from R to the next birthday.

How It Works: A Step-by-Step Example

Come Funziona: Un Esempio Passo-Passo

Suppose B = 1990-02-28 and R = 2025-09-15.

Years: since (09-15) > (02-28), y = 2025 − 1990 = 35.
Months: from Feb to Sep is 7 months, so m = 7.
Days: add 35 years and 7 months to 1990-02-28 → 2025-09-28; since R is 13 days earlier, d = 17 − 30? Instead compute anchor A = 2025-09-28 and daysBetween(A, R) = −13, so we adjust: typically an exact algorithm yields y = 35, m = 6, d = 18. Our calculator performs this borrowing precisely as per the formulas above.

The tool implements these steps reliably, handling varying month lengths and leap years per the Gregorian calendar.

Frequently Asked Questions (FAQ)

How accurate is this age calculator?

It uses Gregorian rules and UTC-based math to avoid daylight-saving offsets. With time-of-day enabled, it is accurate to the second.

Does it support future dates?

Yes. You can see how old you will be on any future “as of” date.

How are leap years and Feb 29 birthdays handled?

The computation follows Gregorian calendar arithmetic. For next-birthday logic on Feb 29 births, this tool uses March 1 in non-leap years by default.

Why might other calculators show different results?

Some rely on local time with DST transitions, causing off-by-one day differences. This tool uses consistent UTC arithmetic for totals.

Is my data private?

All calculations run locally in your browser. Nothing is transmitted or stored.

Can I prefill the calculator via URL?

Yes. Use parameters: ?dob=YYYY-MM-DD&asof=YYYY-MM-DD&time=1. If time=1, you can also pass dobtime=HH:MM:SS and asoftime=HH:MM:SS.

Age Calculator