60 x 60 = 3600 in 1 hour
3600 x 24 = 86400 in a day
8600 x 365 = 31,536,000 in a year
31536000 x 12 = 378,432,000 in 12 years
12 years is 378,683,112 seconds.
The International Astronomical Union definition of a second gives 31,557,600 seconds in a year. That makes 12 years = 378,691,200 seconds. And that is not counting the leap-second corrections that are made from time to time.
394,470,000 seconds
About 1,009,843,200 seconds in 32 years.
20 years = 631,138,519 seconds.