>But the average installation with NTP / ETR running UTC would not even have >to that, would they? NTP will pick up the extra second, and ETR will find >the hardware clock ahead of time and slow it down for 8 hrs to align with >the new wall clock time: UTC incl leap seconds. >If you'd schedule the 1 second correction on the HCP for that moment, the >resulting clock would appear by magic to match the wall clock and your >hardware clock remains to run on AT.
Basically, true. This is referred to as "steering". I'm told that it takes 12 hours to complete the steering for Sysplex Timer and 7 hours for STP. >From someone who knows (it is not me): Customers who have a requirement to remain accurate at all times, and so need to avoid this 7 or 12 hour period that the 1 second leap second is steered out, need to specify leap seconds via the Sysplex Timer or STP. The procedure is to schedule the leap second change at the time the leap second is scheduled to be inserted into UTC, at midnight on June 30, 2015. If that is done, no steering is required as the Sysplex Timer or STP will remain accurate across the insertion of the leap second. Peter Relson z/OS Core Technology Design
