Only recently heard of it. The term apparently refers to jobs in which a worker is expected to work from 9 in the morning to 9 at night, six days a week. Quick arithmetic: 12 x 6 = 72. So a 996 schedule is 72 hours. Sounds like either a sweatshop or office work for workaholics. The very existence of such a casual nickname for such conditions suggests that talk of "work-life balance" and such has become passe. That's unfortunate. I liked that kind of talk.