Command to check the reboot date and time on Linux server
root@server [/]# who -b
system boot 2012-04-24 09:04
root@server [/]# last reboot | head -1
reboot system boot 2.6.18-308.1.1.e Tue Apr 24 09:04 (9+22:24)
root@server [/]#root@server [/]# last -x|grep shutdown | head -1
shutdown system down 2.6.18-308.1.1.e Tue Apr 24 09:04 – 07:30 (9+22:25)
root@server [/]#