You are assuming an American date format. The format of the date may come from 1. Your browser locale. 2. The developer's preference and ignoring the locale.

You are assuming an American date format. The format of the date may come from 1. Your browser locale. 2. The developer's preference and ignoring the locale. 3. The server's configuration (so the operators preference). 4. Guessed based on your current network location. I guess if you are in the US using a US locale it is usually true if you are visiting a US site as almost all of these will select a US locale so it doesn't matter the source, but it is impossible to be sure. And if you live outside of the US or use a non-US locale then at least one of these will frequently return a different locale and you will have little way to know which format is being used.