Digi WAN 3G User Manual page 126

C o n f i g u r e D i g i d e v i c e s
Date and Time settings
The Date and Time settings set the Coordinated Universal Time (UTC) and/or system time and
date on a device, or sets the offset from UTC for the device's system time.
Set Date and Time
Click the Set button to configure the hours, minutes, seconds, month, day, and year on the device.
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).
This value can be used 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 an RTC 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.
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