Quick fix for your update

😎

declare @mycutoff date = '01/01/2020';

select [Date] = CONVERT(VARCHAR(10),CASE WHEN convert(datetime,'7/26/29',1) >= @mycutoff THEN DATEADD(YEAR,-100,convert(datetime,'7/26/29',1)) ELSE convert(datetime,'7/26/29',1) END,103)

Result

26/07/1929