How long must you be separated to be considered divorced?

No amount of separation will result in a divorce. You must obtain a divorce in court in order to legally end a marriage. See the chart at the link for waiting periods for filing divorce actions in the various states.

some states require you to be separated for a period of time before you can file for divorce, and some dont require any certain length of time, but REGARDLESS you have to go through divorce proceedings to be divorced. Get a lawyer!