No bookings of 7th Nov of Sanghamitra has started as it starts from Patna at 2000 h and departs from Mgs at 2337 h. For 8th Nov the booking will open from Mughal Sarai tomorrow..
If he wishes to book from Allahabad on 8th, he can do it today itself as Sanghamitra departs from Ald at 0150 h, which is on 8th of Nov for train starting on 7th Nov..