Google announced its biggest Android Wear update yet on Wednesday, which finally delivers a dedicated custom watch face API that allows developers and designers to build news faces with greater functionality. But it’s not all good news; Google says the custom watch faces you’ve already been using will be pulled if they aren’t updated to use the new API.

The new watch face API is going to make your Android Wear device even greater. Not only will your favorite faces tell you the time, but they’ll also have the ability to display things like the weather, upcoming calendar appointments, and data from the various sensors inside your watch — such as its pedometer.

Google has worked with a number of companies to create faces that demonstrate the new abilities; Specialized has one that displays weather, wind speed, and sunrise and sunset times alongside the actual time, while Surfline’s offering displays local tide information, wave forecasts and conditions, and wind speed and directions.

The new API is a welcome addition to the Android Wear platform for all users, then. There is one downside, though: All custom faces that haven’t been updated to support Google’s new API before January 31 will be removed from Google Play.

“Once the rollout is complete, please transition your existing watch faces to the new API by January 31, 2015, at which point we plan to remove support for watch faces that don’t use the official API,” the company says in its developer guidelines.

This isn’t too surprising — we probably should have seen it coming — but perhaps Google could have given developers more than six weeks to make their changes.

All of the Android Wear watch faces you’ve been using up to this point will need updating, because none of them will have been using Google’s new API. Once they are updated, however, you can probably expect more functionality and better performance.

• ViaAndroid Authority