(bÄt) n. 1. An agreement usually between two parties that the one who has made an incorrect prediction about an uncertain outcome will forfeit something stipulated to the other; a wager: made a bet that it would stop raining before 2:00. 2. An amount or object risked in a wager; a stake: a bet of $50.
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.
The Gregorian year, which is in use in most of the world, begins on January 1 and ends on December 31. It has a length of 365 days in an ordinary year, with 8,760 hours, 525,600 minutes, and 31,536,000 seconds; but 366 days in a leap year, with 8,784 hours, 527,040 minutes, and 31,622,400 seconds. With 97 leap years every 400 years, the year has an average length of 365.2425 days.