Changing objects permission doesn't change its modification date

[romy]

Hi,
I am trying to find out a way to fetch modified permissions.But when i try to change the permissions for eg: for any site,the last modification date changes only for the first time,and remains unaffected when changing the permissions again.
Can anyone help me out please?

[ganeshnaidu]

Could you please let us know whether you got the solution for the above query. Even I also have a similar problem.