We are developing an ExtJS application that is localised to different languages. On startup, Ext locale files are loaded as well to localise Ext components.
en localisation file (ext/locale/ext-lang-en.js) contains wrong default date formats (2 digit year instead of 4 digit). This causes certain years selected in date picker (for example 2060) to be subtracted by 100. (2060 --> 1960), depending on the setting of Date.y2kYear.
Attached patch resolves this issue for en localisation. There might be similar issues for other locale.