## 1 decade has 315,360,000 seconds.

That is, if we go by the typical per-year total, which is 31,536,000 seconds.

However, if we want to be more accurate, we have to take into leap years.

There are 2 or 3 leap years per decade. In the 2020s, for example, there are 3 leap years (2020, 2024, 2028). In the 2030, there will be only 2 (2032, 2036). And back to 3 leap years in the 2040s, and so on.

If it’s leap year, then 1 year has 31,622,400 seconds.

## Seconds in a decade calculation

### Two leap year decades

That means in decades with 2 leap years, we have the following math:

= 8 normal years (seconds) + 2 leap years (seconds)

= 8 * 31,536,000 + 2 * 31,622,400

= **315,532,800**

We note that it’s close, but not exact, to our number mentioned at the top. (It’s 0.05% greater.)

### Three leap year decades

In decades with 3 leap years, we have the following math:

= 7 normal years (seconds) + 3 leap years (seconds)

= 7 * 31,536,000 + 3 * 31,622,400

= **315,619,200**

That’s 0.08% greater than the figure cited at the beginning of this article.

### How do we know the number of seconds in a year?

But let’s also back up for a second because we simply told you the number of seconds in a year.

Let’s go through step-by-step how we got there:

– We know that 1 year has 365 days (366 days during leap year).

– We know that 1 day is 24 hours.

– 1 hour is 60 minutes.

– And we know that 1 minute is 60 seconds.

So if we multiply all that through, we have:

= 365 days per year x 24 hours per day x 60 minutes per hour x 60 seconds per minute

= 31,536,000 seconds per year

Of course, now that you know that there are 86,400 seconds per day, you can calculate how many seconds there are…

– per week

– per year (above)

– per century…

…and virtually every other expanse of time.