CET-4 can't take the place of degree examination. If you are a non-English major candidate, you must take the English degree exam and pass it (if you really want to get a degree).
If you take the self-taught exam for English majors, you must take the second foreign language degree exam to get a degree. You can choose one of Japanese, French and Russian.
The exam time is June every year, and you take the exam at the school where you apply.