Extension in joining from bank

It is the discretion of the Bank, and Bank naturally looks into that course as to whether such knowledge helps the Bank in your functioning.  Your Teaching and bank functioning represents two different aspects and only human sympathy may tilt their decision in your way, and you can never expect that in Bankers.

Finally, members of the forum can not decide a future course of action of an employer, when there is no such law and laid down norm.  You have to rethink about the seniority in joining, as your late reporting may make you junior in your batch and this course is not going to give you food in your career.

That means it is you that has to take a decision considering various pros and cons, and make a request to employer and it is left to employer to decide.

If there was a column in job application, then you might have mentioned in job application the courses etc being pursued.

While you can request to let complete the course it is upto the establishment to accede to your request.

Try by discussing with concerned authority.

Mr.G.L.N.Prasad is right.

Pursue the career in the filed which you like and shall enjoy.