Tektronix SPG8000 Technical Reference page 19

SPG8000 Technical Reference
Leap Second Apply *. Leap seconds, when required, are added on June 30, and/or
December 31, at 23:59:60 UTC. That is, the minute preceding midnight has
61 seconds instead of 60, numbered 0..60 instead of 0..59. This might be an
inconvenient time to make a local clock adjustment. For example, this is during
prime time for the North American Eastern Time Zone. Therefore, the SPG8000
gives the option of deferring the leap second adjustment (if any) on these dates
for up to 24 hours.
DST Change *. Daylight Saving Time (DST) changes twice a year in many time
zones, but some locations do not observe daylight savings time. The SPG8000
has a user programmable DST adjustment to the time zone offset that is made
by adding or subtracting a specified amount from the current time setting. The
scheduled date and time of the change must be programmed into the instrument.
There are two methods for scheduling the DST offset:
Once. In Once mode, the DST offset is applied only once on the date and time
you specify. Set the DST offset to either add or subtract an hour from the time
zone offset, depending on whether DST is starting or ending in your location.
Recurring. In Recurring mode, the DST offset is applied when the DST
START date and time that you specify occurs, and is removed when the DST
END date and time that you specify occurs. The recurring DST offset can
only be a positive number, such as one hour. The DST START/END dates are
formatted as the DST rules are written (e.g., DST starts on the First Sunday in
March at 02:00). For example, to change to daylight savings time, schedule
the system to add one hour to the time zone offset at 02:00:00 (local time) on
March 6, 2011. To return to standard time, schedule the system to remove the
DST offset at 02:00:00 on November 6, 2011. At the scheduled time and date,
the DST change is added to the time zone offset as seen from the instrument
display. You can then program the next scheduled DST change.
VITC may have DST shift already applied. To avoid duplicating DST shifts,
disable the DST SCHEDULER if the time of day reference has DST applied.
Task Scheduler. The task scheduler is responsible for triggering scheduled
events at the appropriate time. This includes DST changes, deferred leap second
adjustments, and triggered alarm outputs.
NTP Server. Option GPS is required to use the NTP server. The SPG8000
includes an implementation of the Network Time Protocol, using the network
interface of the instrument. The NTP server is automatic; when the Master time is
set to GPS and the instrument acquires a valid time, the server will respond with
valid NTP packets to time requests from NTP clients. When the Master time is set
to GPS, the server always responds with UTC time only. It is the responsibility of
the NTP client (PC workstation, file server, etc.) to be configured with the correct
time zone offset. The NTP Server will also respond with valid NTP packets when
the Master time is set to Internal mode.
When using VITC input as the time reference, the NTP service is not available.
System timing
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