table of Contents
1 Introduction Time
1.1 GMT
1.2 UTC
1.3 CST
1.4 IS
2 clock Introduction
2.1 hardware clock
2.2 System Clock
3:00 zone settings
3.1 Display all time zones
3.2 set the time zone
4 Time Set
4.1 Check the system time zone and the current time
1 Introduction Time
1.1 GMT
Greenwich Mean Time. That is Greenwich Mean Time location.
1.2 UTC
Coordinated Universal Time (ie GMT). That is: UTC = GMT + 0. Time container is UTC.
1.3 CST
China Standard Time. CST = GMT + 8.
1.4 IS
Eastern Time. EST = GMT - 5. If the current machine's time zone is New York, then the date is EST.
FIG arrows above the time zone, block represents time. Therefore, taking into account both modified to maintain unity. Otherwise, when it may occur with time zone confusion, just as you get to the United States, but still with the same display GMT watch. As shown below:
2 clock Introduction
2.1 hardware clock
RTC (Real-Time Clock) or CMOS clock, on-board battery power. Only the date time. And the format to UTC.
2.2 System Clock
That system time. General Copy RTC when the system starts, after they run independently. Date not only save time, but also to keep the time zone.
3:00 zone settings
3.1 Display all time zones
timedatectl list-timezones
3.2 set the time zone
timedatectl set-timezone Asia/Shanghai
4 Time Set
Generally do not manually set the time, just need to keep time with the Internet can be a time server synchronization.
yum install ntp // install the ntp service
systemctl enable ntpd // set the boot
systemctl start ntpd // start ntpd service
timedatectl set-ntp yes // start ntp sync
ntpq -p // synchronization time
4.1 Check the system time zone and the current time
timedatectl
Note that the above figure RTC time, is the hardware clock. Save time format is UTC, because consistent with UTC time.