Hello aspirant,

Teacher Eligibility Test (TET) has Current Affairs as one of the topic. Exactly number of months cannot be said, you should have good knowledge about Current Affairs. They can ask any question related to Current Affairs from any year. So update yourself. Daily read newspaper and study General Knowledge books. There are courses in internet you can go through them so that you can cover some topics from there also. Go through previous year's question papers to see how they will ask questions and what type of questions can be asked.

Hope this helps you!!