我的服务器今天突然崩溃并重新启动，我想找出原因。
me@raspberrypi$ last -x
me pts/0 xxx.xxx.xxx.xxx Mon Feb 27 13:43 still logged in
me tty1 Mon Feb 27 12:17 still logged in
runlevel (to lvl 3) 4.4.46-v7+ Mon Feb 27 12:17 - 14:01 (01:43)
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00 - 14:01 (17224+06:01
me tty1 Mon Feb 27 10:17 - crash (-17224+-2:-
runlevel (to lvl 3) 4.4.46-v7+ Mon Feb 27 10:17 - 12:17 (02:00)
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00 - 14:01 (17224+06:01
me pts/0 xxx.xxx.xxx.xxx Sun Feb 26 13:36 - 18:39 (05:03)
我所有的启动信息的时间戳都是 0：
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:19 1970 - Mon Feb 27 16:20:42 2017 (17224+08:20
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:13 1970 - Mon Feb 27 16:20:42 2017 (17224+08:20
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:01 1970 - Mon Feb 27 16:20:42 2017 (17224+08:20
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:13 1970 - Sun Feb 19 03:15:42 2017 (17215+19:15
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:01 1970 - Sun Feb 19 03:15:42 2017 (17215+19:15
reboot system boot 4.4.46-v7+ Thu Jan 1 08:00:01 1970 - Fri Feb 17 12:44:37 2017 (17214+04:44
reboot system boot 4.4.38-v7+ Thu Jan 1 08:00:24 1970 - Sun Feb 5 21:07:30 2017 (17202+13:07
reboot system boot 4.4.38-v7+ Thu Jan 1 08:00:16 1970 - Sun Feb 5 21:07:30 2017 (17202+13:07
为什么总是重启时间Thu Jan 1 08:00？
另外，如何指出为什么会重启、过热或断电？