title: How to make DateAdapter singleton in angular 2 app?
body: <p>I'm developing an angular 7 application with lazy loaded modules. I'm using angular material components as well. I would like to localize and support multiple locales in datepicker component.</p>
  
  <p>I would like to change it globally for the whole application when application language changes. It may be done via DateAdapter.setLocale method.
  However the problem is that if I change it on my root module then it does not change in lazy loaded modules.</p>
  
  <p>Yes, lazy loaded modules have their injector and receive their DateAdapter, where locale is not set to the correct one.</p>
  
  <p>How to achieve that DateAdapter is singleton in the whole app? For other modules there is a forChild() vs forRoot() API, but not for datepicker module.</p>