The default culture of the app should default to the culture of the device.
Put this line of code somewhere in the startup of all Xamarin apps:
CultureInfo.DefaultThreadCurrentCulture = new CultureInfo(CultureInfo.CurrentUICulture.ToString());
Using a Xamarin App.
Note: If this code isn't added, the culture will default to en-US which has the whacky date format that everyone complains about.