What Am I?

I wrote this in 2001 so 9th grade I wanna say

I flow like a river,
I pass like a song.
I give you more,
But you are never satisfied.
I can do anything:
Bring you life, happiness, or wealth,
Death, misery, sadness, or pain.
I change your life.
I know what tomorrow brings,
Where today goes,
I change your life.
And why yesterday came.
I bring you the future.
I brought you the past.
I’m holding today,
What am I?