Hello Yuichiro Tada,
Thanks for bringing this subject to the discussion.
DataGrid component is currently using a handler to set the default value on double click equal to the current date for Date columns.
Nevertheless, I created a sample just to illustrate how you can accomplish that specific behavior, could you please check the sample attached to this message?
As a workaround, you can use the sample as an example. You will need to include a Web Block containing the method that you want to set a new handler for the Dates. (This block is included in the sample attached)

Inside the Web Block you can see that we have a Javascript block containing a setTimeout. We need to wait for the grid to load the group panel otherwise, we will get an error. Feel free to create your own method.

Hope this sample is useful if you need to extend DataGrid to remove the default value on double click for Date columns.
Tiago Pereira