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var
secs: integer;
str: string;
begin
secs := 236;
// SecsPerDay comes from the SysUtils unit.
str := FormatDateTime('nn:ss', secs / SecsPerDay));
// If you need hours, too, just add "hh:" to the formatting string
secs := 32236;
str := FormatDateTime('hh:nn:ss', secs / SecsPerDay));
end;