How long is "overnight"? - (Sep/18/2010 )

Often we need to prepare overnight culture. But how many hours is considered overnight?
Sometimes i prepare my o/n culture in the morning and sometimes evening...

Cultures grow pretty good in abt 8hrs
overnight is usually from 5.00pm to next day 8.am

To me, it's starting the culture at the end of the work day and growing it until the beginning of the next work day. Usually if I'm writing a protocol, however, I'll say "grow overnight for 16 hrs" or "grow overnight 24 hrs" or "grow overnight 12-16 hours". Something along those lines so that it's not too cryptic.

16 hours or thereabouts, I would say 16-18 hours.