Hello Khyati..!!
Hope your preparation for IIT JAM is going well. As per the latest notifications, the Exam authority will conduct the IIT JAM Exam 2018 on 11th February 2018, therefore the IIT JAM Admit Cards will be released in the Second Week of January. For your reference, you can get the official notification at:
Since its end of December already, so you won't have to wait much also. I hope that you have started your preparations for the JAM exam and I wish that you will succeed in this exam.
All the best..!!