using System.Globalization;
………………………………………...................................
CultureInfo cultureRu = new CultureInfo("ru-Ru");
subMain.ДатаРождения = Convert.ToDateTime("25.07.1987", cultureRu);

<div class="form-group">
     @Html.LabelFor(model => model.BirthDate, htmlAttributes: new { @class = "control-label col-md-2" })
     <div class="col-md-4">
          @Html.EditorFor(model => model.BirthDate, new { htmlAttributes = new { @class = "form-control" } })
          @Html.ValidationMessageFor(model => model.BirthDate, "", new { @class = "text-danger" })
    </div>
</div>

            
<div class="form-group">
        @Html.LabelFor(model => model.BirthDate, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-4">
               @{
                      Html.EnableClientValidation(false);
                  }
               @Html.EditorFor(model => model.BirthDate, new { htmlAttributes = new { @class = "form-control" } })
               @Html.ValidationMessageFor(model => model.BirthDate, "", new { @class = "text-danger" })
        </div>
</div>

        [HttpPost]
        public ActionResult Index(DateTest dTest)
        {
            if (!ModelState.IsValid)    // Можно опустить
            {
                // ........................................
                // Что-нибудь делаем, если нужно
                // ........................................
            };

            return View(dTest);
        }

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

        [DisplayFormat(DataFormatString = "{0:dd.MM.yyyy}", ApplyFormatInEditMode = true)]
        [DataType(DataType.Date)]               // Дата без времени
        public DateTime BirthDate { get; set; }
    }

[DataType(DataType.Date)]