Sorting for Time Stamp in Table view

Dear All,

I have added a field with time stamp on the table view. Now I am successfully displaying the date stamp in STRING Format DD.MM.YYYY HH:MM:SS

but when I use sorting it it sorts based on STRING and not on dates,

For example ,

20.10.2014 11:22:22

19.09.2014 11:33:44

18.10.2014 11:55:55

So as you can see it sorted via the string and did not considered the month now in getter if I wrote get_property_as_value  it sorted just fine but now it gets displayed as

20141020112222 and not as per the user's date format set in user profile.

So kindly suggest for this scenario!

Regards,

Dhruvin