Idle Arks features day and night cycles where time passes as your survivors continue to work on the raft. There are four periods of the day: morning, afternoon, evening, and night. When it becomes night time, your survivors will stop what they are doing and turn in for the night.
When you are building the raft, be sure to keep an eye on the time. Once your survivors go to bed, you cannot wake them up at any point until it is morning, so make sure to finish up everything you wanted to before night falls.
To be exact, you should harvest all of your item structures (food farms, trees, etc) before the day is over. During the night, your item structures will probably be ready for harvest when morning rolls around, maximizing profits.