
Division of time
Humans have divided little amounts of time according to their convenience, making it easier for us to track and calculate. It is very important that these time divisions are universal so that people from all over the world agree to them and abide by them.

Different kinds of divisions
100 years is a century, 10 years is a decade. There are 365 days in a year and 2831 days in each month. Every week has 7 days each and a year has approximately 52 weeks. A fortnight is 14 days long. Each day is divided into 24 hours and each hour is divided into 60 minutes. Similarly, every minute is also divided into 60 seconds.

An hour is a smaller unit of time
Compared to a year, an hour is a lot smaller.

Calculation
We have to convert years into days and then into hours. As we know, there are 365 days in a year and each day has 24 hours each. By using that relation, we can easily find out the number of hours in a year. (See How many seconds are there in an hour?)

The math
To calculate the number of hours in a year you need to multiply the number of days in a year by the number of hours each day. Now, we know that in a day there are 24 hours and that there are 365 days in a year.
24hours/day∗365day=8760hours
24hours/day∗365day=8760hours for a year
24hours/day∗366day=8784hours
24hours/day∗366day=8784hours for a leap year 
A sidereal year
Is the time needed by the Earth to complete its orbit around the Sun and it lasts, on average, 365 days, 6 hours, 9 minutes, and 6 seconds.
To know the number of hours in a sidereal year we need to:
Convert 365 days in hours, multiplying by 24:
365∗24=8760hours
365∗24=8760hours
Convert 9 minutes into hours, dividing by 60 (the number of minutes in an hour):
9minutes=(9:60)hours=0,15hours
9minutes=(9:60)hours=0,15hours
Convert 6 seconds into hours, dividing by 60 (the number of seconds in an hour):
6seconds=(6:3600)hours=0,0017hours
6seconds=(6:3600)hours=0,0017hours
Add all the different answers plus 6 hours.
How many hours are there in a year?
How to Calculate Number of Hours in a Year? In one day there are 24 hours and in one year there are 365 days, so on multiplying it, there are 8760 hours in a year.