The 'double leap second' issue has been around a long time and is part of the Posix standard (for some background see http://www.ucolick.org/~sla/leapsecs/onlinebib.html, specifically the section named 'Unix system time and the POSIX standard').
接着Posix标准说冤枉啊，是C89标准先写错的，我也是受害者啊：
之后直接开喷了
The "double leap second" is complete nonsense. It never existed outside the ANSI C standard and never will. It was introduced by the ANSI C 89 committee to document its problems understanding UTC issues. Someone heard that there are two prefered dates for leap seconds per year and this got munched up to the false rumour that UTC days can be up to 86402 seconds long. The definition of UTC, which requires that |UTC-UT1| < 0.9 s all the time, obviously makes double leap seconds mathematically impossible.
