This is indeed strange. Just tested the example provided with
https://docs.microsoft.com/en-us/dynamics-nav/dmy2date-function--date-
This is working like a charm.
I think that you should check with debugger the code where this is coming from and test out with the simple prototype
...
Day := 29;
month := 2;
year := 2020;
outputdate := DMY2DATE(Day, month, year);
MESSAGE(Text1000, Day, month, year, outputdate);
...
If this does not work either then the best bet are:
1. Outdated platform number for your NAV 2017 version. Test using the latest platform file.
2. Year that you pass by is not 2020 but something else
3. Worth checking if you pass 2020 or 1920 or whatever else. Debugger never lies.
