Digi Connect SP User Manual page 56

If offset is set to 00:00, the device's system time and UTC are the same. Setting time and date with an offset of 00:00
results in both UTC and system time being set to the specified value. If offset is not 00:00, setting time sets the system
time to the specified value and UTC is adjusted accordingly.
Offset from UTC
Specifies the offset from UTC for this device. Offset can range from -12 hours to 14 hours. Very rarely, a time zone can
also have an offset in minutes (15, 30, or 45). You can use this value to modify the time and date (generally expected
to be UTC) to compensate for time zones and daylight savings time. Wikipedia provides a list of time zone offsets at:
http://en.wikipedia.org/wiki/List_of_time_zones
On a device with no real-time clock (RTC) and no configured time source, time and date are completely local to the
device and have limited usefulness since they are not persistent over reboots/power-cycles.
On a device with a real-time clock and no configured clock source, time and date are also local to the device but they
are meaningful because they are persistent. The offset option could be useful in adjusting for daylight savings time.
Setting the date and time to standard time and setting offset to 1 whenever daylight savings time is in effect would
serve that purpose.
On a device with a configured clock source, time and date received from a clock source is expected to be UTC. For
users with several devices in different time zones, keeping offset=00:00 might be useful for comparing logs or traces
from different devices, since all would be using UTC.
Time Source Settings
The time source settings configure access to up to five external time sources that you can use to set and maintain
time on the device.
•
Type: Specifies the type of time source for this entry.
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. Use FQDN 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. You can manually set
system time 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 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.
Digi Connect Family and ConnectPort TS Family User Guide 56