update automatically today date

Hi, In Sharepoint 2010 List i'm using "TodayDate" column displaying current date(mm/dd/yyyy).

For Eg:

If i add item on 01-04-2013 it shows

Title     TodayDate

x            01-04-2013 

After that,

If i add item on 05-01-2013 it shows

Title     TodayDate

x            01-04-2013 

y            01-05-2013

But i need output as

Title     TodayDate

x            01-05-2013 

y            01-05-2013

How can  update automatically TodayDate column shows current date only in all items without changing version.?

Thanks in advance.