Not sure this is supported by EVMS (might be a manufacturing term), but we can apply EVMS logic to define this. The earned or planned time would be the number of work hours planned for the project (e.g. 8 hours to paint a wall and there are 4 walls to paint. At the end of 4 days, we should have earned 32 hours) vs. the actual hours spent.
We can do this with irregular hours planned as well. Let's say we planned 15 hours for the first wall, 20 hours for the second wall (it needs some repair before we paint), 15 hours for the third wall, and 25 hours for the fourth wall (it needs repair, extra primer, and a second coat). That means the planned time is 15+20+15+25 or 75 hours. If the actual time was 60 hours, you saved 15 hours over plan.
I don't know how you could derive one from the other since there isn't a direct relationship between the planned time and the actual time.