Date format changes on iPad from yyyy/mm/dd to m/dd/yy

That's good news. I mean, it shouldn't be happening of course. But it's not affecting workflows, so that's a good thing. As a general rule, all bets are off when it comes to forms data on mobile platforms. You can never count on it working consistently, or sometimes at all, across all the various ways PDF files can be viewed on mobile operating systems.

If you're fortunate enough to have things working the way you want with one workflow and one way to view mobile PDFs, you want to stick with it. Especially if you can drive how mobile clients view your files. Testing may help you discover more options to offer clients, but if you can channel them to what you know works, you have the best chance of successfully implementing your PDF forms plan.

Note: you want to encourage your clients not to update their Acrobat Reader applications on iPad until you've tested it and can confirm it will keep working for you. You can never do that with the general public, but if you have a controlled group within your organization, you've got a much better chance to prevent rude surprises.

Your iPad default settings have one way of showing time, and it works on your desktop just fine so it's not built into the PDF form data. I know of no setting that affects how time is displayed in Adobe Reader through either app preferences within the app or in Apple settings. TL/DR: You got me. I can't begin to tell you why it's happening on your iPad with Adobe Reader, unless there's a toggle switch inside some other setting for some other app that's changing it for you. I know that's maddening, and it's cold comfort to say that you're lucky that it's the only problem with your PDF form on the iPad.

But it's working, and that's the main thing, right?

Randy