How many seconds are there in a decade?

315,532,800

http://wiki.answers.com/Q/How_many_seconds_are_there_in_a_decade

Calculation (ignoring leap years for the time being):

60 (seconds in a minute) * 60 (minutes in an hour) * 24 (hours in a day) * 365 (days in a year) * 10 (years in a decade) = 315,360,000

No link for the above, the explanation should be sufficient.

Why is it less than pgpm10's answer? So far, this calculation doesn't include leap years. A proper answer needs to know how many leap years there are in the decade. There might be either 1 or 2 of them, each of which adds an extra day to the calculation. If the first or second year of the decade is a leap year, then there will be two days more than the basic calculation, giving 315,532,800 seconds. If the third or fourth year of the decade is a leap year, there will be only 1 extra day, giving 315,446,400 seconds.

Again, I provide no link. I assume everyone knows that there is a leap year every fourth year (unless the year is a century that is divisible by 4). The only issue, really is whether the decade under consideration has two or three leap years in it.

This morning I see an error in my previous calculations! If Year 1 is a leap year, so will Years 5 and 9, giving a total of THREE in the decade, not the two managed to count yesterday! The decade will have either two or three leap years, giving a total of 315,532,800 or 315,619,200 seconds.

This calculation also ignores the thorny issue of exactly how long a day is - depending on whether you use sidereal days or solar days. When you measure in seconds, over 10 years, there is a significant difference.


"A day of exactly 86,400 SI seconds is the astronomical unit of time (the second is not preferred in astronomy).

For a given planet, there are two types of day defined in astronomy:
* sidereal day - a single rotation of a planet with respect to the distant stars
* mean solar day - average time of a single rotation of a planet with respect to its star.

For Earth, the sidereal day is about 3 minutes 56 seconds shorter than the solar day. In fact, the Earth spins 366 times about its axis during a 365-day year, because the Earth's revolution about the Sun removes one apparent turn of the Sun about the Earth."

https://en.wikipedia.org/wiki/Day

And to complicate things further, some decades (taking "decade" to mean "10 year period") only have one leap year. The next such decade is 2093-2103.

And that takes you back to the total I posted for the case of only 1 leap year! (Why would you want to use seconds to measure such a long period of time, anyway?)