what is insert value pattern for datetime field

Question

I have table call ProductStatistics

in that table column types are like following

    public string CreatedBy { get; set; }
    public Nullable<System.DateTime> CreatedDate { get; set; }

but once I try to insert value like following

Insert into ProductStatistics(CreatedBy,CreatedDate) Values('20',25/01/2016)

I can see wrong CreatedDate value inserting instead of true value here,

what should I change here