When people talk about having time, they are not aware that it's an idiom for sparing time to do it. They talk about having time as in having money, like it's something that one can pull out of a drawer.
If I don’t have time for something, I don’t have the remaining hours to spend on it, given the time I’ll spend doing other things.
So no, you never just have time you're not using anyway. You're always using all of your time. On what is a matter of priorities.
However, if you would spend 19--21 watching a TV series, or twiddling your thumbs, you can choose to take that time to do something else.