We can use the who command with the -b flag to check Linux last reboot date and time. Root privileges are not necessary to perform this check.
$ who -b
system boot 2020-08-29 06:39
To check the date and time of all previous Linux system reboots, we can use the last reboot command. This gets the information from the /var/log/wtmp file.
$ last reboot
reboot system boot 4.15.0-117-gener Mon Sep 14 16:54 still running
reboot system boot 4.15.0-117-gener Mon Sep 14 16:51 - 16:54 (00:02)
reboot system boot 4.15.0-117-gener Mon Sep 14 16:49 - 16:51 (00:01)
wtmp begins Mon Sep 7 04:31:42 2020
