Shutdown checkpoints are stored in USERDATA/system/shutdown-checkpoints. The  files are named �checkpoint-UNIXEPOCH�, and the files are in plain text. The timestamp in file name aligns with Modified time of file.� The shutdown checkpoints keep a log of when the phone was shutdown/rebooted. Something worth noting is� that the time is stored in local time and can also provide a reason for the shutdown (e.g., dead battery). Kevin Pagano wrote a blog on this:  https://www.stark4n6.com/2022/01/shutdown-checkpoints-in-android-12.html 

At the time of writing this, ALEAPP was one of the only tools to parse this artifact.