When was Satan cast down?

I don't have the answer yet (if I will this side of heaven I don't really know). But look at this passage.

Isaiah 14:12-15 (New International Version)

12 How you have fallen from heaven,
O morning star, son of the dawn!
You have been cast down to the earth,
you who once laid low the nations!

13 You said in your heart,
"I will ascend to heaven;
I will raise my throne
above the stars of God;
I will sit enthroned on the mount of assembly,
on the utmost heights of the sacred mountain. [a]

14 I will ascend above the tops of the clouds;
I will make myself like the Most High."

15 But you are brought down to the grave,
to the depths of the pit.

So, Satan (the morning star, and son of the dawn) seems to have had aspirations related to the creation (stars, mount, mountain, clouds) before his fall (make myself like the Most High).

I'll keep searching. Let me know what you think.