Given history to date, the leap second information needed by knowledgeable,
concerned clients is, in its entirety:
1972-06 1972-12 1973-12 1974-12 1975-12 1976-12 1977-12 1978-12 1979-12
1981-06 1982-06 1983-06 1985-06 1987-12 1989-12
1990-12 1992-06 1993-06 1994-06 1995-12 1997-06 1998-12
2005-12 2008-12
2012-06
These are the months at the ends of which leap seconds were inserted.*
I'm confident that a way of getting the information to such clients can be
developed.
It may be prudent to wait and see if the status of the leap second changes
in 2015;
a change may obviate the need for leap second updates (though not the need
for information on past leap seconds).
@dashdashado
*This ignores the possibility of skipped seconds, which have yet to occur
in the wild.
It also ignores niceties such as New York City, which at least once
"observed" the leap second at midnight New York time
rather than midnight UTC, making for a ball drop countdown of
"Three...two...one...leap...Happy New Year!"
