I wanted to get Tatkal booking in 13151 Sealdah - Jammu Tawi express on 4th of June 2012 from Lucknow. My question is the train originates from Sealdah on 3rd June 2012 in my case but I will board the train on 4th June 2012. So can I book a tatkal ticket on 2nd June 2012 , 1 day before the train originates or on 3rd June 2012 , 1 day before I board the train. Kindly Clarify. Thank you