system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] What kind of hours do you work on a Federation starship? I know there are three eight-hour shifts, but do you have a standard 40-hour work week? More/less?
gpt
Some ships run 4 shifts, especially when training or maintaining a high state of readiness. Deep Space Nine also switched to four shifts.

Most crew would work six or seven days per week, and anywhere from 12 to 24 hours per day. 

Most people would also have some other job that they do around their station watches. Like Troi sees patients when she's not on the bridge, Crusher is an administrator (and occasional bridge officer) as well as a physician, Wesley was in school, and so on.

A lot of "free time" is going to be spent on training and testing, and a lot of "recreation time" is going to be spent on exercising and bodily maintenance. 

Researchers may keep bankers' hours, but most of them are usually eager to do more work too. It's a luxury just to be on a starship.

Instead of time off, what most crew really look to achieve is a relatively stable schedule that lets them develop a routine. Of course, if they come upon a planet or starbase then they can usually find time to take some leave.