Hi Tomek,
Thanks for your update.
By default Grid column type will be set based on your first value of the column from the dataSource. If you have using the value is the date string and set the column type as date, Grid will convert the value as date string to the date object value.
But, the Grid can preforming the action like Filtering, Searching, Grouping, Sorting, etc., based on the original value of the Grid data Source. So we suggest you to need defined date object value for the date column.
And the valueAccessor is used only for the display purpose and we cannot perform any Grid actions like Filtering, Searching, Grouping, Sorting, etc., to this column. So, we are unable to perform the value while updating through valueAccessor. This is the behavior of EJ2 Grid.
Note : The Grid can perform the actions like Filtering, Sorting, Searching, Grouping, aggregates, etc., are only based on the column field and its dataSource value.
So we suggest you to change the date value as date object (new Date()) in your dataSource.
Please get back to us if you need further assistance.
Regards,
Praveenkumar G