You likely can't get a safe amount of entropy from the available resolution in time. For example, even assuming nanoseconds, that's only log(10^9) bits of entr

You likely can't get a safe amount of entropy from the available resolution in time. For example, even assuming nanoseconds, that's only log(10^9) bits of entropy if you can guess what second (not that hard, may even be public). That's nowhere near enough. I'd also doubt that many ways you try to get a nanosecond resolution time actually have that resolution, there's probably discrete steps of lower resolution.