2^31 is about 2 * 10^9.
> If you have interrupts at 1 Megahertz, (10**6), you still have a big
> enough number for 10*25 seconds of interrupts.
10^6 is about 2^20. 10^25 is about 2^83.
> There are about 10*5 seconds in a day...so we can encode years and years
> and years (how long has your linux system been running).
2^31 / 86400 is about 25000. 2^31 seconds is a little over 68 years.