if a new item will added to datasource in the grid, then new values of item are not render in define format. (in e.g "date")
Miss i a command on data before or after pushing?
Here is my example code : http://plnkr.co/edit/WIoAU0ZJOIus4pDblZpb?p=preview
For some reason, the grid will apply the formatting from the column definition during initialization but does not when adding a row directly to the dataSource after initialization...you have to essentially do it yourself, otherwise it just gets treated as a string.
It seems like a bug(or inconsistent behaviour) but there may be a good reason for it. This is how I have dealt with it in my own code when adding rows programmatically.