[m4nu3l]

> But isn't it possible to have a local flow of time?

You can use a clock to measure time, but I think it's better to say that matter and energy move through time, just like they move through space instead of saying that time flows, because flow implies time which makes the definition circular.

So I would just say that if you consider any frame of reference you can define time with respect to it. But still there is no real "present" in time just like there is no "here" in space. You can just take any point in space and say it's your origin.