Dateformatのフォーマットキャラクタについて

Dateformatのフォーマットで利用できるキャラクタはバージョンにより異なる。

The format methods in this class implement a subset of Unicode UTS #35 patterns. The subset currently supported by this class includes the following format characters: acdEHhLKkLMmsyz. Up to API level 17, only adEhkMmszy were supported. Note that this class incorrectly implements k as if it were H for backwards compatibility.

v18以降	acdEHhLKkLMmsyz
v17以前	adEhkMmszy

参考

http://developer.android.com/intl/ja/reference/android/text/format/DateFormat.html
http://qiita.com/amay077/items/b33603b958a4d0eedc8a