When you’re out at sea, the things that determine how you spend your day are whether you are steaming to a location to do research, the weather, and whether your equipment is working.
If all those things are working, then what determines how you spend your day (on this cruise at least) is what day of the Cycle you are on, and how many replicates of each experiment you need to do at that Cycle. Our cycles last three days, and are spatially determined by where the sediment traps and drifters take us.
What else determines how you spend your day is whether you need to take your samples during the day or at night, every 6 or 12 hours, or right at sunrise and sunset as the plankton migrate from the bottom to the top of the water column.
What doesn’t determine when you work is what day of the week it is. There’s no sense of the weekend, or a 40 hour work week. So it’s Friday night, but no one cares. There’s still science to be done.