Digi WAN 3G User Manual page 127

Time Source Settings
The time source settings configure access to up to five external time sources that can be used to set
and maintain time on the device.
Type: Specifies the type of time source for this entry.
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– sntp server: The device uses its SNTP client to poll the NTP/SNTP server, specified by
the FQDN, for time.
– cellular: The device polls the cellular service for time.
Interval: Specifies the interval in seconds between polls of a time source. Interval can

range from 1 second to 31536000 seconds. If more than one time source is specified,
time sources with shorter intervals have greater influence on the device's time than do
sources with longer intervals.
FQDN: Specifies the fully-qualified domain name or IP address for the time source. The
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FQDN is used only if the time source is SNTP.
The only time source that is guaranteed to be present on all products at all times is the system
clock. It counts uptime and displays system time as the UNIX Epoch (00:00:00 on January 1,
1970) plus uptime. Any source that is not the system clock is considered an external source. This
includes the RTC.
Devices which have an RTC but have no external time sources configured will display system time
as the UNIX Epoch plus the time since power was initially applied to the device until system time
is set manually. System time can be set manually via the CLI, Web UI, etc. Once system time is set
manually, the RTC will continue to maintain system time but, due to variations in the accuracy of
the RTC, system time can diverge from external time.
Specifying an external time source allows the device to compare its system time to the time
reported by the configured time sources and make appropriate adjustments to system time. This
allows system time to stay consistent over long durations.
The polling interval for an external source establishes its priority relative to other sources; the more
samples taken from a time source, the greater influence that time source has on system time.
Any time adjustment will update the RTC automatically. All time sources are assumed to be UTC.
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