1 billion seconds is a significant birthday or anniversary, being about 4 months shy of 32 years. 1 billion seconds is 31 years, 251 days, 13 hours, 34 minutes, 54.7843 seconds. But note that these are 365-day years, so you have to adjust for leap years. Remember, a leap year adds 1 day at the end of February on years that are divisible by 4, unless they're also divisble by 100, except when it's also divisible by 400.