uses SysUtils, Classes;
var
TxtList : TStringList;
today : tdatetime;
begin
TxtList := TStringList.Create;
if fileexists('File/log.txt') then TxtList.LoadFromFile('File/log.txt');
today := now;
TxtList.Add(datetostr(today)+', '+timetostr(today));
TxtList.SaveToFile('File/log.txt');
TxtList.Free;
end.