Just for reference. Here are the numbers on the nines:
One nine: 36 days 12 hours (36 1/2 days)
Two nines: 3 days 16 hours (3 2/3 days)
Three nines: 8 hours 45 minutes (8 3/4 hours)
Four nines: 1 hour (actually, 52 minutes 36 seconds)
Five nines: 5 minutes (or 5 minutes 15 seconds or 315.576 seconds)
I'm always hearing these numbers and have taken them for granted. I finally decided to calculate them. These numbers are based on a 365.25 day year (with the standard 24 hours comprised of 60 minutes, each minute being in duration 60 seconds).
Oh, and just for fun:
Six nines: half a minute (slightly more)
Seven nines: a smidge over 3 seconds.
Eight nines: don't even think about it. (slightly less than a third of a second)
Nine nines: You're crazy..........