Going off of Job 38:4-7,

Quote
Where were you when I laid the foundation of the earth? Tell Me, if you have understanding, who set its measurements? Since you know. Or who stretched the line on it? On what were its bases sunk? Or who laid its cornerstone, when the morning stars sang together and all the sons of God shouted for joy?

Here the "sons of God" refer to the angels, which is clear from the prologue to Job in 1:6: "Now there was a day when the sons of God came to present themselves before the LORD, and Satan also came among them." It would seem the angels were created no later than the first day of creation. The exact timing is not revealed in Scripture, but my inclination is that they were created when God created heaven (since that is the dwelling-place of angels). Scripture doesn't say when Satan fell, but evidently it wasn't long after his creation if indeed the angels were created on the first day.

Kyle

I tell you, this man went down to his house justified.