[LEAPSECS] Computing platform that recognizes leap seconds.

[Gerard Ashton]

There have been allusions to computer systems other than POSIX which 
recognize leap seconds. I thought I would point out a partial example of 
one.

The z/Architecture Principles of Operation (descendant of the 
System/370) explains in chapter 4 the operation of the time of day clock.

The publication is available at
http://www-01.ibm.com/support/docview.wss?uid=isg2b9de5f05a9d57819852571c500428f9a

One of the bits is incremented each SI microsecond, and the epoch is 1 
January 1900 (sort-of UTC). Whole leap seconds are counted after 1 
January 1972. Before that, the time scale considers every day to consist 
of exactly 86,400 seconds. I found the explanatory text rather 
confusing, and derived my impression of how it operates by examining the 
values in the various tables.

I am not able to explain how the value of the time of day clock is 
carried through programming libraries and finally displayed to people.