How to give system default date timestamp into db in code first approach MVC

public static DateTime Now { get; set;}

public int Id { get; set; }
        [Required(ErrorMessage = "First Name is required")]
        [StringLength(50, MinimumLength = 3)]
        [Display(Name = "First Name")]
        public string FirstName { get; set; }

  //[Required(ErrorMessage = "Last Name is required")]
        [StringLength(50, MinimumLength = 0)]
        [Display(Name = "Last Name")]
        public string LastName { get; set; }

     [Required(ErrorMessage = "Age is required")]
        [Range(typeof(int), "18", "60", ErrorMessage = "Age must be between 18 and 40")]
        public int Age { get; set; }



       [Display(Name = "Email Address")]
        [Required(ErrorMessage = "Email Address is required")]
        [StringLength(60)]
        [DataType(DataType.EmailAddress, ErrorMessage = "Invalid Email Address")]
        public string Email { get; set; }


       [Display(Name = "Mobile Number")]
        [StringLength(10)]
        [Required(ErrorMessage = "Mobile Number is required")]
        [RegularExpression("[6-9][0-9]{9}", ErrorMessage = "Mobile Number must 
        begin with 6,7,8 or 9")]
        public string MobileNumber { get; set; }

        public DateTime DateOfBirth { get; set; }



       [StringLength(20)]
        public string PlaceOfBirth { get; set; }
        [StringLength(20)]
        public string Nationality { get; set; }

    [Required(ErrorMessage = "Password is required")]
        [StringLength(10)]
        [DataType(DataType.Password)]
        public string Password { get; set; }



       [Required(ErrorMessage = "Confirm Password is required")]
        [DataType(DataType.Password)]
        [StringLength(10)]
        [Display(Name = "Re-Enter Password")]
        [Compare("Password")]
        public string ConfirmPassword { get; set; }