Calculator WiFi usage on Marshmallow, Nexus 5? What? I have not used the calculator app.  I also don't know why it would be using the wifi or any kind of external data.  Yet behold, below:



I flashed 6.0 recently and restored some apps from an old backup, but nothing that looked like calculator.  Should I be concerned, or is this a known thing?
First off,
   They no longer uses Floating point arithmetic al which I read from a blog.
Second, 
    Marshmallow have introduced a lot of new features in its calculator which does uses internet for floating/decimal calculations for user-friendly UI and other touch gizmos. Currently its a kind of prototype, so it'll be downloading a bit for the updates but you can always disable the app from system settings.
You can see the new features from this site - http://www.androidpolice.com/2015/06/12/android-m-feature-spotlight-the-stock-calculator-app-has-been-overhauled-no-longer-uses-floating-point-arithmetic/