I find this stuff incredibly boring.

Stolen from What’s Wrong With Turkey

Most languages have this covered; there are functions that allow you to read or write dates and numbers appropriately for various cultures. In .NET, for example, it’s the difference between these two calls:

int.Parse("32,768", System.Globalization.NumberFormatInfo.InvariantInfo);

The "invariant" culture is every American programmer’s secret dream realized: we merely close our eyes and wish away all those confusing languages and cultures and their crazy, bug-inducing date and number formatting schemes in favor of our own. A nice enough dream while it lasts, but instead of rudely asking your users to "speak American" through the invariant culture, you could politely ask them to enter data in ISO international standard format instead.