If you ever wanted to figure out how old you are in seconds you need a mathematical equation. But to put into more simple terms, take how many seconds are in 24 hours, multiply that by how many days there are in a year (352) and then multiply that by how many years old you are. For example if you were 20 years old you would be 608,256,000 seconds old. there is 86400 seconds in 24 hours times 352 days a year, times 20 years to get your answer.
It is easy to find out how many seconds old you are thanks to one online website! Simply answer a few questions and the site will tell you how many seconds you have been alive! You can find more information here: http://www.time-for-time.com/howold.htm