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Age in Seconds Calculator

Created by Davide Borchia
Reviewed by Komal Rafay
Last updated: Jan 18, 2024

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 with Omni!

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.

How do we define a second? A second is the sixtieth part of a minute and, in turn, equals 1/36001/3600 of an hour (there are 36003600 seconds in an hour). We can go even higher — we'll do it later.

We just gave you the first definition of the second, how historically the units originated. For this, we need to thank Babylonians: their base-60 numerical system opened the doors to the subdivision of an angle in 6060 minutes of arc and each minute in 6060 seconds of arc. The Iranian polymath Al-Biruni translated this idea from angles into time, dividing each hour in the same fashion.

How long is a second?

For centuries the second remained an extremely variable unit: hours hadn't a fixed duration, and the second followed. With the introduction of the first mechanical clocks, this changed, and our timekeeping abilities upgraded immensely!

The first scientific definition of a second came in the first half of the XIX century when the unit of time was linked to the duration of the solar day:

1 s=1 d86, ⁣4001\ \text{s}=\frac{1\ \text{d}}{86,\!400}

In 1950 metrologists (the scientists of measurements) decided to base the second on the more stable duration of the sidereal year, with the rather cumbersome equation:

1 s=1 y31, ⁣556, ⁣925.97471\ \text{s}=\frac{1\ \text{y}}{31,\!556,\!925.9747}

Humanity's timekeeping abilities reached, at that point, accuracy higher than 1 part in 10810^8. But we can do better: just in 1967, the definition changed again: the second is now described as the duration of 9,129,631,7709,129,631,770 complete transitions between two hyperfine energetic levels of the stable cesium-133 isotope.

The uncertainty of the best realizations of the second can be of 15×101215\times10^{-12} seconds per year. To put this number in context, if we started that clock at the moment of the Big Bang, it would not have lost a single second!

How to calculate the age in seconds?

To find your age in seconds, the best choice is to count the number of days between your date of birth and the chosen date. How to do so?

  1. You can count: good luck!
  2. You can convert the date into the Julian date number (JDN), a unique indicator for each date.
  3. You can use a calculator! 😉

Let's analyze number 2 for the sake of correctness. To calculate an age in seconds, take a couple of dates in the format D/M/Y\text{D/M/Y}. Now, calculate the Julian date number using this terrible formula:

JDN=1461(Y+4800+M1412)4+367(M212M1412)123Y+4900M14121004+D32,075\footnotesize \begin{align*} JDN\!& =\! \frac{1461\!\cdot\!\left(Y+4800+\left\lfloor \frac{M-14}{12}\right\rfloor\right)}{4}\\ \\ &+\frac{367\!\cdot\left(M-2-12\!\cdot\!\left\lfloor\frac{M-14}{12}\right\rfloor\right)}{12}\\ \\ &-\frac{3\!\cdot\!\frac{Y+4900\left\lfloor \frac{M-14}{12}\right\rfloor}{100}}{4}\\ \\ &+D-32,\!075 \end{align*}

Now you should have something like this: for the date 09/15/199709/15/1997, the JDN is 2,450,6962,450,696.

When you have the two JDNs, one for the final date and one for the initial one, subtract them. The result is the number of days elapsed between the two dates.

What to do now? Multiply the result by the number of seconds in a day: 86,40086,400.

Examples of calculations of ages in seconds

Let's try to find your age in seconds. Were you born on the 19th of June 1992? What a coincidence!
The JDN at the moment of your birth was 2,448,7922,448,792. Take another date, let's say the 21st of July 2012: the JDN is 2,456,1292,456,129.

Calculate the difference between the dates:

2,456,1292,448,792=7,337\footnotesize 2,\!456,\!129-2,\!448,\!792=7,\!337

Multiply the result by 86,40086,400 to find your age in seconds:

7, ⁣33786, ⁣400=633, ⁣916, ⁣8007,\!337\cdot86,\!400=633,\!916,\!800

That's a lot! Or not? After all a second is pretty fast.

What's the age of the Universe in seconds? Good question. We can only give an approximation: it's impossible to set a date for the Big Bang! Time itself began around 13.813.8 billion years ago. Multiply by 365365 to find the number of days, then by 86,40086,400 to find the age of the Universe in seconds:

86,40036513.8×109=4.35×1017\footnotesize 86,\!400\cdot365\cdot13.8\times10^{9}=4.35\times10^{17}

More than the age in seconds calculator


How many seconds are in a day?

There are 86,400 seconds in a day. This number comes from the structure of our days:

  • There are 60 seconds in a minute;
  • There are 60 minutes in an hour; and
  • There are 24 hours in a day.

Multiply these number:
24 × 60 × 60 = 86,400

How do I calculate my age in seconds?

To calculate your age in seconds, follow these steps:

  1. Calculate the difference between your date of birth and the current date in days.
    • To do so, you can convert the dates into the Julian day number.
  2. Multiply the difference between the dates by 86,400 to find your age in seconds.
  3. Do you want to be more precise? Consider only the hours effectively passed in the first and last day!

What is my age in seconds if I was born on the 2^^nd^^ of February 1998?

Assuming that today is the 6th of July 2022, you are X seconds old.
To calculate this result:

  1. Calculate the number of days between the dates. It is 8,921 days.
  2. Multiply the number by 86,400 to find your age in seconds:
    8,921×86,400 =76,982,400

Why are there 60 seconds in a minute?

A minute lasts 60 seconds thanks to the Babylonians: they introduced this division with their base-60 numerical system more than three thousand years BC. However, we had to wait until the 11th century to see the introduction of the minute and the second as units of time. The number 60 remained because it has many divisors: 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30.

Davide Borchia
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