Age in Seconds Calculator

When counting time, seconds come first: with our age in seconds calculator you will learn how to find your age in seconds, and much more. Learn what a second is, why we use seconds, and how to calculate how many seconds passed between two dates.

What is a second?

The second is the basic and uncontested measurement unit of time. It's a time you can easily count (one, two, three...) and marks a flow we can appreciate with our eyes without difficulty.

Historically, a second is the sixtieth part of a minute and equals 1/3600 of an hour (there are 3600 seconds in an hour). The Babylonians, with their base‑60 numerical system, subdivided angles in 60 minutes and each minute in 60 seconds; Al‑Biruni translated this idea from angles into time, dividing each hour the same way.

How long is a second?

For centuries the second remained variable because hours had no fixed duration. Mechanical clocks changed that. The first scientific definition linked the second to the solar day:

1 s = 1 d / 86,400

In 1950, metrologists based the second on the sidereal year:

1 s = 1 y / 31,556,925.9747

Since 1967, the second is defined by cesium‑133: the duration of 9,129,631,770 transitions between two hyperfine energy levels of its ground state. The best realizations have uncertainties near 15 × 10⁻¹² seconds per year.

How to calculate the age in seconds?

To find your age in seconds, count the number of days between your birth date and a chosen date, then multiply by 86,400. Ways to get days between dates:

• Count them manually (not recommended!)
• Convert dates to the Julian Day Number (JDN) and subtract
• Use this calculator 😉

JDN formula for a date D/M/Y:

JDN = 1461 × (Y + 4800 + ⌊(M − 14)/12⌋) / 4
    + 367 × (M − 2 − 12 × ⌊(M − 14)/12⌋) / 12
    − 3 × ⌊(Y + 4900 + ⌊(M − 14)/12⌋) / 100⌋ / 4
    + D − 32,075

For example, JDN for 09/15/1997 is 2,450,696. Subtract JDNs to get days, then multiply by 86,400 to get seconds.

Examples of calculations of ages in seconds

Born on 19 June 1992 (JDN 2,448,792) and checking on 21 July 2012 (JDN 2,456,129):

2,456,129 − 2,448,792 = 7,337 days

7,337 × 86,400 = 633,916,800 seconds

The age of the Universe (~13.8 billion years) in seconds (approx.):

86,400 × 365 × 13.8 × 10⁹ ≈ 4.35 × 10¹⁷ seconds

More than the age in seconds calculator

Seconds aren’t always the best unit for chronological age. Try related calculators:

• Age in weeks
• Age in years
• Age in years, months, and days
• Age in days
• Age in hours
• Age in minutes
• Age in months
• Days old

FAQs

How many seconds are in a day?
24 × 60 × 60 = 86,400.

How do I calculate my age in seconds?
Compute days between your birth date and today (e.g., with JDN), then multiply by 86,400. For extra precision, account for the partial first/last day hours.

If I was born on 2 Feb 1998, how many seconds old am I on 6 Jul 2022?
There are 8,921 days between those dates. So 8,921 × 86,400 = 770,774,400 seconds.

Tip: This page calculates it for you. Enter your birth date above.