Do you want session relevance that will give you all computers that appear to be powered on right now? If so, you can approximate that by returning computers whose last report time is within a certain time period.
If you want to know what computers were on at a specific time period, then that would require using the power tracking data, which I’m not sure if it actually keeps the specific computer, or just aggregate data, so I don’t know if it possible or not.
Could you provide more explanation as far as what you are looking for?