How to show time when a box is checked?

I have a basic work ticket sheet setup (from a template), and when someone submits the form, it records the created date AND time without issue. But i also have a "resolved date" column, and all i want that to do is record the date AND time when i change the dropdown in "ticket status" to resolved.

This seems like it should be a very basic ability, but for some reason i cant get any date columns (other than created date) to show a time at all. In another thread someone mentioned a formula for time, but i cant figure out how to apply that in this situation: =[Due Date]@row + ""