During what stage of the cell cycle is DNA copied?

DNA isn't really copied, it's more so split into 2 parts.

DNA is split into 2 parts during mitosis, more exactly the 5th stage called anaphase. chromosomes, which hold DNA< are split into 2 (genetically identical) groups, and each respective group goes to one spindle or another, readying for the last phase of mitosis and eventually cytokinesis.