概念

RTC Time

RTC（Real Time Clock，实时时钟）也叫做 CMOS 时钟，它是 PC 主机板上的一块芯片（或者叫做时钟电路），它靠电池供电，即使系统断电也可以维持日期和时间。

操作

┌[root@localhost] [/dev/pts/0] 
└[~]> timedatectl
               Local time: Tue 2023-04-25 16:48:08 CST
           Universal time: Tue 2023-04-25 08:48:08 UTC
                 RTC time: Tue 2023-04-25 08:48:08
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

时区和时间的准确性

修改时间

date -s  "2023-04-25 16:00:00"

修改时区

┌[root@localhost] [/dev/pts/0] 
└[~]> tzselect 
Please identify a location so that time zone rules can be set correctly.
Please select a continent, ocean, "coord", or "TZ".
 1) Africa
 2) Americas
 3) Antarctica
 4) Asia
 5) Atlantic Ocean
 6) Australia
 7) Europe
 8) Indian Ocean
 9) Pacific Ocean
10) coord - I want to use geographical coordinates.
11) TZ - I want to specify the time zone using the Posix TZ format.
#? 4
Please select a country whose clocks agree with yours.
 1) Afghanistan          29) Kyrgyzstan
 2) Antarctica           30) Laos
 3) Armenia          31) Lebanon
 4) Azerbaijan           32) Macau
 5) Bahrain          33) Malaysia
 6) Bangladesh           34) Mongolia
 7) Bhutan           35) Myanmar (Burma)
 8) Brunei           36) Nepal
 9) Cambodia             37) Oman
10) China            38) Pakistan
11) Christmas Island         39) Palestine
12) Cocos (Keeling) Islands  40) Philippines
13) Cyprus           41) Qatar
14) East Timor           42) Russia
15) French Southern Territories  43) Réunion
16) Georgia          44) Saudi Arabia
17) Hong Kong            45) Seychelles
18) India            46) Singapore
19) Indonesia            47) Sri Lanka
20) Iran             48) Syria
21) Iraq             49) Taiwan
22) Israel           50) Tajikistan
23) Japan            51) Thailand
24) Jordan           52) Turkmenistan
25) Kazakhstan           53) United Arab Emirates
26) Korea (North)        54) Uzbekistan
27) Korea (South)        55) Vietnam
28) Kuwait           56) Yemen
#? 10
Please select one of the following time zone regions.
1) Beijing Time
2) Xinjiang Time, Vostok
#? 1

The following information has been given:

    China
    Beijing Time

Therefore TZ='Asia/Shanghai' will be used.
Selected time is now:   Tue Apr 25 16:41:39 CST 2023.
Universal Time is now:  Tue Apr 25 08:41:39 UTC 2023.
Is the above information OK?
1) Yes
2) No
#? 1

You can make this change permanent for yourself by appending the line
    TZ='Asia/Shanghai'; export TZ
to the file '.profile' in your home directory; then log out and log in again.

Here is that TZ value again, this time on standard output so that you
can use the /usr/bin/tzselect command in shell scripts:
Asia/Shanghai

重启corn

systemctl restart crond

写个测试脚本

57 16 * * * touch /tmp/111

看看文件是否创建成功