Yeah, basically what Redfox said. I don't have time right now to walk you through all of them, but I'll do the first one:
There are 3600 seconds in an hour, 24 hours in a day, and 365 days in a year. So 1 year = (3600*24*365) seconds.
1,000,000,000/(3600*24*365) = 31.71