How do you test your app for Iñtërnâtiônàlizætiøn compliance? I tell people to store the Unicode string Iñtërnâtiônàlizætiøn into each field and then see if it is displayed
There is more to internationalization than unicode handling. You also need to make sure that dates show up localized to the user's timezone, if you know it (and make sure there's a way for people to tell you what their time zone is).
One handy fact for testing timezone handling is that there are two timezones (Pacific/Tongatapu and Pacific/Midway) that are actually 24 hours apart. So if timezones are being handled properly, the dates should never be the same for users in those two timezones for any timestamp. If you use any other timezones in your tests, results may vary depending on the time of day you run your test suite.
You also need to make sure dates and times are formatted in a way that makes sense for the user's locale, or failing that, that any potential ambiguity in the rendering of dates is explained (e.g. "05/11/2009 (dd/mm/yyyy)").