@using System.ComponentModel.DataAnnotations;

    <EditForm Model="ModelData">
        <DataAnnotationsValidator />
        <ValidationSummary />
        <br /><br />
        <span>Not nullable</span> @ModelData.Date<br />
        <Telerik.Blazor.Components.TelerikDatePicker @bind-Value="ModelData.Date" Min="DateTime.MinValue" Max="DateTime.MaxValue"></Telerik.Blazor.Components.TelerikDatePicker><br /><br />
        <span>Nullable</span> @ModelData.Date2<br />
        <Telerik.Blazor.Components.TelerikDatePicker @bind-Value="ModelData.Date2" Min="DateTime.MinValue" Max="DateTime.MaxValue"></Telerik.Blazor.Components.TelerikDatePicker><br /><br />
    </EditForm>

@code  {

    public MyModel ModelData { get; set; }

    protected override void OnInitialized()
    {
        ModelData = new MyModel();
    }

    public class MyModel
    {
        public string Name { get; set; }

        [Required(ErrorMessage = "Non nullable required")]
        public DateTime Date { get; set; } = DateTime.Today;

        [Required(ErrorMessage = "Nullable required")]
        public DateTime? Date2 { get; set; } = DateTime.Today;
    }
}