When were angels created?
We know that God created the angels before He created the world. According to the account in book of Job, the angels (all the sons of God) are worshipping God as He was creating the world:
"Where were you when I laid the foundations of the earth? Tell Me, if you have understanding. Who determined its measurements? Surely you know! Or who stretched the line upon it? To what were its foundations fastened? Or who laid its cornerstone, when the morning stars sang together, and all the sons of God shouted for joy?" (Job 38:4-7).
If we consider the many tasks of angels, it is very possible that God created the angels shortly before He created mankind because one of their functions is to be "ministering spirits sent to serve those who will inherit salvation" (Hebrews 1:14). They had to exist before the Garden of Eden because Satan (formerly called the angel Lucifer) was already present in the garden in his rebellious and fallen condition.
Another important fact to consider is because angels worship God around His throne (Revelation 5:11-14), they could very well have been in existence long before God created the earth. We really can't be sure exactly when the angels were first created by God; but we do know they were created before He created the world.