修改Centos7的系统时区的两个方法！

# timedatectl
Warning: Ignoring the TZ variable. Reading the system's time zone setting only.

Local time: Mon 2016-11-21 01:52:42 EST
Universal time: Mon 2016-11-21 06:52:42 UTC
RTC time: Mon 2016-11-21 06:52:42
Time zone: America/New_York (EST, -0500)
NTP enabled: n/a
NTP synchronized: no
RTC in local TZ: no
DST active: no
Last DST change: DST ended at
Sun 2016-11-06 01:59:59 EDT
Sun 2016-11-06 01:00:00 EST
Next DST change: DST begins (the clock jumps one hour forward) at
Sun 2017-03-12 01:59:59 EST
Sun 2017-03-12 03:00:00 EDT

# timedatectl  set-timezone Asia/Shanghai
Warning: Ignoring the TZ variable. Reading the system's time zone setting only.

Local time: Mon 2016-11-21 14:52:59 CST
Universal time: Mon 2016-11-21 06:52:59 UTC
RTC time: Mon 2016-11-21 06:52:59
Time zone: Asia/Shanghai (CST, +0800)
NTP enabled: n/a
NTP synchronized: no
RTC in local TZ: no
DST active: n/a
[root@localhost ~]#

TZ='Asia/Shanghai'; export TZ