The bug that originally started this topic was fixed a long time ago, so you have not discovered the same bug. In fact, you are not even using the same dialog, since the Fill with Value dialog doesn’t have a Morph button.
You may have discovered a different bug, but you also may simply be using an incorrect formula. If you are using a lookup( from one date field to another, you should not be using the datepattern( function – that function will convert the date into text, and you don’t want that, you want to keep it as a date. I don’t really have enough information to go on, but I think your formula should simply be:
If you want assistance with this, please tell us what the programming code you tried was. We can’t see your screen and we have no idea what you actually tried. However, I’ll take a wild guess from the rest of your post, perhaps the correct code would be something like this: