To calculate the number of seconds in a year, you need to account for the different lengths of years depending on whether it's a leap year or not.

In a regular, non-leap year, there are 365 days, each consisting of 24 hours, 60 minutes, and 60 seconds. So, the calculation would be:

365 days/year × 24 hours/day × 60 minutes/hour × 60 seconds/minute = 31,536,000 seconds/year

In a leap year, there are 366 days, due to an additional day in February (February 29th). So, the calculation would be:

366 days/year × 24 hours/day × 60 minutes/hour × 60 seconds/minute = 31,622,400 seconds/year

Therefore, in a regular year, there are 31,536,000 seconds, and in a leap year, there are 31,622,400 seconds.