Timestream DAYNAME alternative to limit aggregation to weekdays

I am looking for an option to have aggregation over timeseries to be performed only for weekdays, like Monday, Tuesday and etc. I tried DAYNAME function but it doesn't seem to exist. Is there an alternative to that function or any other way to achieve what I am after?

Would be also interesting to find out how to get aggregation limited from 06:00 to 16:00 every day for example, but this might be a separate question.