Linux/Unix systems keep the details of the previous reboot. You may also need to know when the system was rebooted last.
Check Last Reboot
Mostly Linux/Unix systems provide the last command, which provides us the history of last logins and system reboots. Run last reboot command from the terminal, and you will get the details of last reboots.
last rebootreboot system boot 2.6.18-92.el5 Sat Feb 11 12:00 (12+22:51) reboot system boot 2.6.18-92.el5 Sun Feb 5 12:57 (5+21:17) reboot system boot 2.6.18-92.el5 Sat Jan 28 15:58 (13+18:16) reboot system boot 2.6.18-92.el5 Thu Jan 26 17:15 (15+17:00) reboot system boot 2.6.18-92.el5 Mon Jan 9 13:40 (32+20:35) reboot system boot 2.6.18-92.el5 Sun Jan 8 15:50 (33+18:24) reboot system boot 2.6.18-92.el5 Sat Dec 24 12:58 (48+21:17)
The above output shows that the system was last rebooted on Feb 11 at 12:00 PM.
Check System Uptime
Additionally, you can also use uptime command to find the system uptime from last booted. Just open the terminal on your system and type uptime and hit enter.
uptime10:57:54 up 12 days, 22:57, 2 users, load average: 0.00, 0.00, 0.00
as per above output, the system is running from 12 days, 22 hours and 57 minutes.