It is bewildering isn't it, well in our specific case it is not the "local settings", and we're also seeing machines within individual countries who use 5 different formats.
What we discovered more recently is also that the same log, on one machine can have a mixture of all these date formats; in the _same_ file (that's insane).
We have moved to mostly disable mcafee on a few thousand machines that were giving us issues, so it's no longer a active problem but it would still be interesting to know the root cause.
Good luck and do tell if you figure it out on your own!
This is a very complicated area of code, so I'm not surprised if you're seeing oddities.
Please, if you want to see the behavior improve for your specific use case - since the complexities of the code try to cater for "everybody" which is probably doomed to fail but still, to have it behave the way You want, provide the relevant details to our Support folk and we'll see what we can do. And if we can't achieve what you're looking for, we can give you better insight into why you're getting the results you're seeing.