2.4 form helper iso 8601

CakePHP is not just "American" anymore, its a globally used framework. Therefore, after already complying to ISO standards regarding localization I recommend that it complies with the hour format used internationally.
The 12 hour system is only used by a handful of countries and the ISO standard implies that the 24 hour system is the one that should be used as default: "ISO 8601 uses the 24-hour clock system".

See http://en.wikipedia.org/wiki/ISO_8601

Doc update and migration guide entry coming up.