Error 1 Operator '!=' cannot be applied to operands of type

    if(dateofbirth.Year.ToString()!=1900)
    SendSMS(txt_DOB.Text.Trim());
    else
    if(Weddingday.Year.ToString()!=1900)
    SendSMS(txt_wedding.Text.Trim());

   form the above when i run i show the  error message as follows;

Operator '!=' cannot be applied to operands of type 'string' and 'int'    .

please correct my code and send.