Following the TOTP standard, this is a third party time-based code generator. It'll work with any service that adheres to the standard, including Google and Microsoft services, but two factor codes from many others. It's also well done, if incredibly minimalist.

From the Store description:

OTP Manager generates 2-step verification codes.

Works with all services supporting the TOTP standard, including:

• Microsoft two-step verification
• Google two-factor authentication
• Dropbox
• Evernote
• Github

and many more.

Features:

• Generates codes without need for internet access
• Support for multiple accounts
• Support exporting account data
• Add account data via link or QR code
• Account data is stored on disk encrypted

It works too - TOTP always seems a little like magic, but I guess with device clocks now being always kept in sync with 'Internet time' that time-based codes are now the practical way to go.

Here's OTP Manager in action:

All TOTP two factor systems let you set up a linked device via QR code. In this case I'm getting Google to show me the two factor code and using OTP Manager on my Lumia 950 to recognise it...

The QR code equates to a long random 'secret' and you get to see it (or enter one manually) in the main form, before 'saving' for use; (right) When needed, you get 30 second codes, auto-regenerated as needed, to help you log in to the relevant service. The bar at the bottom animates to let you know roughly how long you've got left with this code before it expires.

You can grab OTP Manager UWP here in the Store.