Dear Reader,

Hope you are doing well

It's totally upto to the institutions you are going to join that what are there rules of joining date to be called whether it's the date of admission or the day when you paid the fees of counselling for institution.But in 90% cases,the joining date is considered as the date when you paid the counselling fees to the institution.

Hope above information helps to clear all your doubts regarding this.

Have a good day and great future ahead..