.NET ASP C# - Datetime.now return back 2 days when insert

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C#

ASP.NET

.NET

DateTime

Hello my friend.
My project have a big mistake. when i insert a new data, my Datetime.now is returned bad values. Example, when insert: 05/20/2015. It will be back 2 day: 05/18/2015.
This is my Code.

Data:

   public bool add(Bill_DTO bill_dto) 
{ 
    try 
    {
        SqlCommand _cmd = new SqlCommand('INSERT INTO BILL('ID_BILL,TIMECOMING') VALUES(@ID_BILL,@TIMECOMING)')
        _cmd.Parameters.Add("ID_BILL", SqlDbType.NVarChar).Value = bill_dto.ID_Bill;
        _cmd.Parameters.Add("TIMECOMING", SqlDbType.Datetime).Value = bill_dto.TimeComing; 
        dp = new DataProvider(); 

        return dp.ExecuteNonQuery(_cmd) > 0;
    } 
    catch (Exception ex) 
    { 
        throw ex; 
    } 
    finally 
    { 
        dp.CloseConn(); 
    } 

Business:

Bill_DTO bill_dto = new Bill_DTO();
Bill_DATA bill_data = new Bill_DATA();
bill_dto.TimeComing= DateTime.now;
bill_data.add(bill_dto);

Thanks for your help !!!