7.2. to change system date/time
date
e.g. date -s month/day/year
# date -s 1/18/2008
time
e.g. date -s hour:minute:second
# date -s 11:12:00
writing CMOS
# clock -w
更新网络时间
ntpdate - client for setting system time from NTP servers
$ sudo ntpdate asia.pool.ntp.org
21 May 10:34:18 ntpdate[6687]: adjust time server 203.185.69.60 offset 0.031079 sec
$ sudo hwclock -w