Hello,
Well from what I see the problem is not ODWEK, but merely the way the day format is done in the Application.
You said, that in the second example, you use "%m/%d/%y", but that means : MM/DD/YYYY, and you are sending MM/DD/YY, which means in CMOD "%m/%d/%Y", please note the capital "Y".
At least, this is from what I see in what you are showing us.
Concerning the first example, I think the format was something like "%e", because the format that CMOD is expecting is something in the line "%d XXX %Y", where XXX is the short month form (I have put XXX because I don't know the % code for the short month form!).
Now, why it works with arsload, and not with ODWEK, this is not clear... what release of ODWEK are you using? I mean the full version number: V9.5.0.4 ??