You can read more about the supported dataSource types in an editable Kendo UI Gridhere.
That said, to format the column as a date you can use a Kendo UI Template. This will ensure the required rendering, but as the "bd" field it is of type "object" you will need to specify the editor for the column:
This way on editing the "bd.dt" field will be parsed as a date correctly. This article goes over the requirements for defining a custom grid editor and you can see a runnable demo here. For your scenario you can define a DatePicker editor via the datePickerEditor function:
Please don't hesitate to reach out if more questions arise.
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