Coming to the total number of hours in a year, obviously it would be a huge number as we have so many days and there after 24 hours in each day. For calculating the total Numbers of hours we can start from the minimum unit like second. We know 1 minute has 60 seconds and of course 1 hour is of 60 minutes. Now, as we know a day has 24 hours. So a week has 24 * 7 that is 168 hours. The year being defined as 31,556,925.9747 seconds, this is quite a big number; if we divide these seconds to 3600 seconds then we get result in hours. There are 8765.8127 hours of 3600 seconds each in one year, by multiplication of days, there are 8766 hours in a Julian year.
A month of 30 days has 720 hours and a month of 31 days has 744 hours. It is quite shocking to know that there are 8784 hours in a year of 365.24 days that is an approximate value. Generally the values differ in a leap and a non-leap year, for example we can take a leap year which has 366 days and there are 24 hours in a day. Therefore 366 * 24 that is 8784 hours in a leap year.