Hola.
Un modo puede ser,
Código Delphi
[-]
function AmPmTo24(const ampm: TTime): string;
var
F: TFormatSettings;
begin
F := FormatSettings;
try
with FormatSettings do begin
LongTimeFormat := 'hh:mm:ss';
TimeSeparator := ':';
Result := TimeToStr(ampm);
end;
finally
FormatSettings := F;
end;
end;
Ejemplo de uso:
Código Delphi
[-]
procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessageFmt('%s%s%s',[AmPmTo24(StrToTime('11:59:59 AM')), #10,
AmPmTo24(StrToTime('11:59:59 PM'))]);
end;
Saludos