Clock appClock is Time tool that is open source under the Apache-2.0 license. Deskclock is a fork of the AOSP clock, so it offers all its functions:
* count-down "timer" (aka "tea timer")
Additionally, it adds:
* "Power-off alarm function" (alarm will ring with phone off, Snapdragon phones only, tested on LineageOS and should work on all AOSP ROMs; currently does not work on MIUI).
*Flip and shake action for alarm
VIBRATE: enable vibration when the alarm sounds
DISABLE_KEYGUARD: alarm notification when the screen is turned off
POWER_OFF_ALARM: make the alarm sound when the phone is off (supported devices only)
RECEIVE_BOOT_COMPLETED: register alarms on device start
USE_FULL_SCREEN_INTENT: needed with Android 10+ to show the alarm screen when an alarm fires
A more detailed description can be found in the repository's README.