Correct me if I'm wrong, you need an ADP version (or better B4xDateTemplate) which shows 28.04.2563 as Tuesday and not Monday, right?
Internally it should "convert" between 2020 and 2563 or simply cheat, showing 2563 but "reasoning" using 2020 instead..
In other words, your special copy will read and manage 28.04.2020 but will show 28.04.2563; so for the input/output.