I tested the scenario for a fresh DNN 4.8.0 installation and it worked.
There is an another story behind this issue which I didnt mentioned in my original post.Pardon me for not doing that.
I am using a , my own custom login module which uses the "UserController.UserLogin()" method and which I thought might taken care of the culture of the current thread of the application.But that wasnt the case it seems.
SO I will revisit my code and try to rectify the issue.
If you have any suggestions , really appreciate of it.
Thank you all for your valuable responses to this thread and I will change the status of this thread once I rectify the issue.
Thank you
Indika