Android persist.sys.boot.reason.history

https://cs.android.com/android/platform/superproject/+/master:system/core/bootstat/bootstat.cpp;l=920?q=BootReasonAddToHistory

static auto mark = time(nullptr);
auto mark_str = std::string(",") + std::to_string(mark);
auto marked_system_boot_reason = system_boot_reason + mark_str;

the number after “," looks like simply from time(nullptr)

$ adb shell getprop persist.sys.boot.reason.history
cold,28
cold,29
cold,27
reboot,factory_reset,1653457758