When a person works one day, then resigns & joins another company in the middle of the week, the previous days on the new job calendar will show "n/a", but when the day is over, the day you joined will be shown as "X".

This gives the impression that the person missed work that day, yet they did work at the other job & their hard worker progress is not reset.

I suggest that if the person has worked that day when they switch, it automatically sets that day to "n/a".