Hey vishal!

The candidates who have got admission in B.tech first year at IIT MADRAS will be called for some admission procedure in the last week of july , perhaps monday only. Then , the whole procedure will take your time from 9 to 5 . Then , there will be an orientation programme on the next day. And the still next day , there will be your departmebnt orientation in which you will be introduced to your department labs and faculty.

After all this   you academic classes will start from the first monday of august. This is the most tentative day. There can be slight variations in these dates according to the college arrangements.

Hope it helps!