Описание тега angular-i18n
NoneAngular -i18n is part of the Angular framework, which provides i18n features like localization (dates, number, percentages, and currencies), text translations, pluralization and alternative text. For the older AngularJS (1.x) web framework, use the angular-translate tag.
Angular 2+ provides its own tool for internationalization. It already supports many features, but misses some major features like lazy loading, translation outside templates etc. Those features will be available in Angular 6+.
Since Angular is under development the implementation of i18n still is in progress an can be tracked on this GitHub issue: #16477