+1 my immediate thoughts about the date parts was this sounds a lot like localisation things that are totally normal and seen everywhere.

But there are some wrinkles - why only two timezones and not others? E.g. US-vs-rest-of-word month-vs-day etc.

Could just be some bad tree-shaking or simply a left over bug/merge issue if I am being generous.

If I was going to put secret stenography things in my models I'd just do it in the model response rather than a relatively low bandwidth date stamp in the SI.