If the DateTimeProperty is defined as (may contain null):
public DateTime? WorkedDate { get; set; }
Use this format:
grid.Column("WorkedDate", "Last Worked On",
format: (item) => item.WorkedDate != null
? item.WorkedDate.ToString("MM/dd/yy") : "", canSort: true)
Otherwise, if it is defined below (cannot be null), it will have either the actual date or the .MinDatedefault value.
public DateTime WorkedDate { get; set; }
Use format:
grid.Column("WorkedDate", "Last Worked On",
format: (item) => item.WorkedDate != DateTime.MinValue ?
item.WorkedDate.ToString("MM/dd/yy") : "", canSort: true)