Hi,
I tried your suggestion in my project and it works for all the cultures I have tried except "da_DK" which is the one I need 
When setting a date I get the following exception:
Unhandled exception rendering component: One or more errors occurred. (String '2023-07-26T00.00.00.000Z' was not recognized as a valid DateTime.)
System.AggregateException: One or more errors occurred. (String '2023-07-26T00.00.00.000Z' was not recognized as a valid DateTime.)
---> System.FormatException: String '2023-07-26T00.00.00.000Z' was not recognized as a valid DateTime.
at System.DateTimeParse.Parse(ReadOnlySpan`1 s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
at System.DateTime.Parse(String s, IFormatProvider provider, DateTimeStyles styles)
at Radzen.QueryableExtension.GetColumnFilter[T](RadzenDataGridColumn`1 column, String value, Boolean second)
at Radzen.QueryableExtension.ToFilterString[T](IEnumerable`1 columns)
at Radzen.Blazor.RadzenDataGrid`1.InvokeLoadData(Int32 start, Int32 top)
at Radzen.Blazor.RadzenDataGrid`1.Reload()
at Radzen.Blazor.RadzenDataGrid`1.LoadSettings(DataGridSettings settings)
at Radzen.Blazor.RadzenDataGrid`1.OnAfterRenderAsync(Boolean firstRender)
--- End of inner exception stack trace ---
I also tried checking out the source code for Radzen and changed the culture in your demo:
and I get the same exception:
Unhandled exception rendering component: String '2023-07-13T01.00.00.000Z' was not recognized as a valid DateTime.
System.FormatException: String '2023-07-13T01.00.00.000Z' was not recognized as a valid DateTime.
at System.DateTimeParse.Parse(ReadOnlySpan`1 s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
at System.DateTime.Parse(String s, IFormatProvider provider, DateTimeStyles styles)
at Radzen.QueryableExtension.GetColumnFilter[T](RadzenDataGridColumn`1 column, String value, Boolean second) in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\QueryableExtension.cs:line 468
at Radzen.QueryableExtension.ToFilterString[T](IEnumerable`1 columns) in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\QueryableExtension.cs:line 150
at Radzen.Blazor.RadzenDataGrid`1.InvokeLoadData(Int32 start, Int32 top) in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\RadzenDataGrid.razor.cs:line 1725
at Radzen.Blazor.RadzenDataGrid`1.Reload() in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\RadzenDataGrid.razor.cs:line 1675
at Radzen.Blazor.RadzenDataGrid`1.OnFilter(ChangeEventArgs args, RadzenDataGridColumn`1 column, Boolean force, Boolean isFirst) in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\RadzenDataGrid.razor.cs:line 621
at Radzen.Blazor.RadzenDataGrid`1.ApplyFilter(RadzenDataGridColumn`1 column, Boolean closePopup) in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\RadzenDataGrid.razor.cs:line 756
at Radzen.Blazor.RadzenDataGridHeaderCell`1.ApplyFilter() in C:\Users\W87538\RiderProjects\radzen-blazor\Radzen.Blazor\RadzenDataGridHeaderCell.razor:line 191
at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)