Because it isn't the 32nd day of the month? In about 180 million years we will be up to a 25 hour day, due to the tides from the moon slowing the earth down. So, about every 2083 years we add a second to each day.
On Thu, May 4, 2017 at 11:42 AM, Paul Gilmartin <[email protected]> wrote: > On Thu, 4 May 2017 07:53:24 -0500, Dana Mitchell wrote: > >>This has been discussed before and is explained very well in this IBM techdoc: >> >>https://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP102081 >> >>Depending on if you need to be exactly on time after the leap second occurs, >>or can tolerate taking a while to 'smear' the time to the new value, STP >>gives you the choice of spinning whilst waiting for an extra leap second to >>be inserted (Category 1) or slowly steering the time (Category 2): >> >>STP will begin to slowly steer the mainframe time to the new value. It takes >>approximately 7 hours for STP to steer out a one second delta. >> > That depends on *not* running the (E)TOD clock at the TAI rate and with > the 10-second offset that is otherwise IBM's recommendation. > > Amazon and Google have the pragmatic approach of a smear centered on the > leap secoond, making the maximum deviation from UTC a half second rather > than a full second. I suppose this could be achieved with the HMC/STP by > using Google or Amazon as a reference. If they come to agree on the interval. > > Steering the TOD clock would break applications (are there any?) that depend > on microsecond accuracy of STCK. > > Making multiple microscopic adjustments to CVTLSO throughout a smearing > interval has other sorts of complexity. > > Why does a 24-hour adjustment for a leap year cause less disruption than > a single leap second? > > -- gil > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
