Gigasecond

A gigasecond (symbol: Gs) is one billion seconds. That is about 31.7 years. It can be written as 109 seconds.
3.16 Gs is about 1 century (100 years). 31.6 Gs is about 1 millennium (1000 years).
This page lists times of between 1 and 1000 gigaseconds, or between 31.7 and 31,700 years.