uses System.SysUtils, System.DateUtils;

var
  NowValue, Yesterday, Tomorrow: TDateTime;
  NextMonth, NextYear: TDateTime;
begin
  NowValue := Now;

  Yesterday := IncDay(NowValue, -1);
  Tomorrow := IncDay(NowValue, 1);
  NextMonth := IncMonth(NowValue, 1);
  NextYear := IncYear(NowValue, 1);

  WriteLn('now: ', DateTimeToStr(NowValue));
  WriteLn('yesterday: ',
    DateTimeToStr(Yesterday));
  WriteLn('tomorrow: ',
    DateTimeToStr(Tomorrow));
  WriteLn('nextMonth: ',
    DateTimeToStr(NextMonth));
  WriteLn('nextYear: ',
    DateTimeToStr(NextYear));
end.