A positive leap second will be introduced at the end of June 2015
Why don't we just switch from UTC to TAI and put the leap seconds in our localtime offsets?  It makes all the problems go away, or else reduces them to problems we've already solved for handling daylight saving time.If you think about it, leap seconds are no different than daylight saving time.  The only differences are that daylight saving time usually has 1-hour granularity and is occasionally redefined by your government, where leap seconds have 1-second granularity and are occasionally redefined by Mother Nature.We already know how to deal with repeating seconds and minutes (alternatively, with minutes or hours that are too long).  Those happen during daylight saving time changes, but the ambiguity disappears when switching to UTC.  We already record timestamps and communicate with UTC, applying a localtime offset for display or user input.  That's a solved problem.Further, we know how to change the localtime offset.  Most timezones do that twice a year.  We also know how to handle timezone definition changes because ignorant legislatures sometimes modify when the daylight saving time switches occur.So, why don't we switch from UTC to TAI as an underlying time standard?  When UTC leap seconds occur, we can treat them somewhat like a government redefining its timezones.  US Eastern Time then changes from "TAI-05:00:35/TAI-04:00:35" to "TAI-05:00:36/TAI-04:00:36".If two UTC clocks are synchronized, then one accounts for a leap second and the other misses it, the clocks will no longer be synchronized.  If they were TAI clocks, they would still be synchronized and both would still record and communicate correct timestamps.  It's just that one would display localtime incorrectly.  But, you would immediately know that was the case when you see that the offset is a second behind.  Missing a leap second would be like having your computer is set to the wrong timezone, and would be just as easy to fix.