A gigasecond is equivalent to 1,000,000,000 (one billion) seconds, which is about 31.7 years.
16 years = 504,910,816 seconds.
There are 1,452,576,000 seconds in 46 years.
There are, roughly, pi times 10 million seconds in a year (the actual number is 31,556,926, but "pi times 10 million" is close and easier to remember). So just multiply that by that large number of years, and there's your answer. So 1,000,000,000 years equals 3.1556926 × 1016 seconds.
There are 1,358,724,800 seconds in 43 years.
There are 1263141040 seconds in 40 years
10 years = 315,569,260 seconds.
18 years is about 568,036,800 seconds.
1,000,000 years = 31,556,736,000,000 seconds
There is about .000000126755 years in 4 seconds.
9 years is about 284,018,400 seconds.
About 1,009,843,200 seconds in 32 years.