We have an issue with the way our web server is set up that means we cannot use ionicons. It's a cloud platform and not a real web server so there is no easy way around this problem.
To work around this all our ion-icons use the src attribute to point at the icon svg file directly.
In the date picker this means that the next / previous month buttons are invisible as the arrow icons fail to resolve properly.
It would be great if you could add a configuration property to allow us to define custom image src to use for these buttons!