https://www.techradar.com/news/wear-os-watches-could-soon-last-longer-thanks-to-an-enhanced-battery-saver-mode

Smartwatches typically don’t last as long as we’d like, but Google looks to be improving that situation for devices running Wear OS, as they’ll soon have access to a new enhanced battery saver mode.

The mode is available now as part of the latest Android P developer preview, and according to the Android Developers blog it will turn off the touchscreen, radios and tilt to wake. Pressing the side button will show the time and, based on the image below, seemingly also the date and a red battery icon to indicate the mode you’re in.