This is a short example on how to quickly format a current day

delphi_date_format.pas

uses
System.DateUtils;

procedure FormatDateToString(): string;
var
  CurrentDate: TDateTime;
  FmtStngs: TFormatSettings;
begin 
  { As a bonus using IncDay will get you any day from current date, such as yesterday would be IncDay(Now, -1) }
  CurrentDate := IncDay(Now, 0); 
  FmtStngs := TFormatSettings.Create('en-US');
  FmtStngs.ShortDateFormat := 'yyyy-MM-dd';
  Result := DateToStr(CurrentDate, FmtStngs);
end;