A long time ago (15+ years) I worked on a VAX. If memory serves, it was a MicroVAX 3900. I don’t recall ever seeing this unit of measure mentioned in the docs, but I may have. It’s the “microfortnight” and reading about it always makes me laugh. From the Jargon file:
1/1000000 of the fundamental unit of time in the Furlong/Firkin/Fortnight system of measurement; 1.2096 sec. (A furlong is 1/8th of a mile; a firkin is 1/4th of a barrel; the mass unit of the system is taken to be a firkin of water). The VMS operating system has a lot of tuning parameters that you can set with the SYSGEN utility, and one of these is TIMEPROMPTWAIT, the time the system will wait for an operator to set the correct date and time at boot if it realizes that the current value is bogus. This time is specified in microfortnights!
Wikipedia’s article on microfortnights has a bit more info
The joke is in having a rather large unit (fortnight) combined with a fractional SI prefix (micro) to counteract that. The practical purpose is to discourage setting such parameters without some thought. The unit was selected because the time is only approximately one second, being established by some near-infinite loops rather than a real clock unit (which isn’t active at the time), and rather than field complaints about this being “not exactly a second”, the unit was invented.
Heck, I don’t even have to be reading it to laugh about it. Just thinking about it makes me laugh.