This application provides access to common settings and tools to make managing the system date and time easy.
Date & Time
The settings on this tab control the date, time and zone of the system clock.
When selecting a different time zone, the calendar and clock controls will reflect the change. The system clock will not be altered until Apply is pressed.
The hardware clock, also known as a realtime clock (RTC), keeps track of the time when the system is off. When the system is booted, the time is read from the Hardware Clock.
The Time zone for the Hardware Clock determines whether the hardware clock is set according to UTC or the Local time zone. UTC is recommended, unless the system is also used with an operating system that requires the hardware clock time set to the local time zone.
The buttons in the Time transfer section copy the system clock time across to the hardware clock, and vice versa.
If Update the drift is selected when copying from System Clock to Hardware Clock, the drift factor for the hardware clock is updated. It is automatically unselected once the operation is complete, and should not be selected again for at least 4 hours from the last drift update.
The Hardware Clock tools can be used to tune and maintain the hardware clock:
- The Read the Hardware Clock tool queries the hardware clock for information on how it is currently set up.
- The Drift Adjust tool applies systematic drift corrections to the hardware clock, if the drift factor is known.
The output from these tools will be placed in the text box under the buttons.
Changing the time zone for the Hardware Clock
The recommended method for correctly changing the time zone for the hardware clock, is to press Apply immediately after selecting the time zone (UTC or Local). Check the contents of the text box in Hardware Clock tools to ensure everything is correct. If the time is different, the hardware clock may have been adjusted for the change in time zone.
If the new time is incorrect, set the system clock to the correct time. You can use Update Now in the Network Time tab for this. Once the system clock is set correctly, press System Clock to Hardware Clock.
Drift factor calculation
For a useful drift factor to be calculated, first go to Network Time and update the system clock using NTP. Then with Update the drift selected, press System Clock to Hardware Clock. Perform these steps again after at least 4 hours. The longer the time between drift calculations, the more precise the drift factor will be.
The system clock can be maintained with the help of other systems that communicate using the Network Time Protocol (NTP). The settings on this tab control how the NTP client service behaves.
When Automatically update the System Clock with NTP servers is selected, the NTP servers that are on the list will be periodically checked and, if necessary, the system time will be adjusted. The Update Now button can be used to manually adjust the system clock in line with the NTP servers on the list.
The NTP list contains a list of servers that are used for updating the time. The Type is one of the following:
- Pool. A persistent association with a number of remote servers. Multiple Pool items are required for this to work.
- Server. A persistent association with the specified remote server or local radio clock.
- Peer. A persistent symmetric-active mode association with the specified remote peer. Unlike Server and Pool the remote peer can also be synchronized to the local clock.
The Address must be a valid IP address (IPv4 or IPv6) or a domain. The item is only used if there is a tick in the box next to its address, otherwise it is ignored.
The Options can specify additional flags and options for the server.
To apply the settings, /etc/ntp.conf is parsed and altered. This application does not cover the entire scope of this file, so for more advanced configurations, edit this file manually.