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In the  enterprise Linux network, it is necessary to keep track of  server shutdown and reboot time. Most of you may have used the shutdown /  reboot command.

Show listing of last reboot / shutdown date and time

last command  searches  back  through the file  /var/log/wtmp (or the file designated by the -f flag) and displays a  list of all users logged in (and out) since that file was  created.  The  pseudo user reboot logs in each time the system is rebooted.  Thus last  reboot will show a log of all reboots since the log file was created.

Shutdown (halt) system immediately

Type the command as follows:
 

However on production server above command is dangerous as it won't  allow users to save files/work/data. It is better to give users a  warning and then take down the box:

Schedules shutdown command

You can also schedules shutdown with shutdown command
# shutdown 1:00 SERVER DOWN"
# shutdown 18:00 SERVER DOWN"
First one will shutdown server at 1:00 AM and second will be at 6:00 PM  (it uses 24 hrs clock format)

How do I find out serve shutdown / reboot time?

Now most exciting part, how will you find out when system was last  rebooted or halted (shutdown). Often new UNIX/Linux admin don't find out  solution easily. When ever you issue shutdown/reboot command a entry  created in /var/log/wtmp file, don't open or modify this binary data  file. You can read this log file with the help of last command.

Display list of last reboot entires

Use last command as follows:
last reboot  | less

Display list of last shutdown entires (includes run level changes):

Type the command as follows:
  last -x| less

Or even better try:
 

Note file /var/log/wtmp is log file which stores previous login  sessions and use last command to  access information. Same commends  works on FreeBSD and other UNIX like oses.