Amazon is smearing their clocks for 12 hours each side of this June's leap second, so that the clocks will run smoothly but will be 0.5 s off when the leap second is inserted. This affects only their management console and backend systems; user EC2 instances are expected to do the usual NTP dance. See: Clarke G. Amazon cloud to BEND TIME, exist in own time zone for 24 hours. The Register 2015-05-19. http://www.theregister.co.uk/2015/05/19/amazon_cloud_leap_second/ This is similar to the leap smear that Google has been doing since a 2005 leap second hit some of their servers, and the WSJ article says that financial markets in Japan, South Korea and Australia are also doing different variants of leap smear. Although leap smear ought to be standardized (why would people want to dilute differently in different countries or companies?), a previous attempt at standardization didn't take. See: Kuhn M. UTC with Smoothed Leap Seconds (UTC-SLS). 2011-09-16. http://www.cl.cam.ac.uk/~mgk25/time/utc-sls/ A higher-tech approach to deal with leap seconds would be to launch yourself into space at sufficient velocity so that when you return, relativistic time dilation would cause your POSIX clock to match an earthbound UTC clock. Unfortunately this requires time travel one second into the future, whereas the current human record-holder, Sergei Krikalev, has traveled only 23 ms into the future, and it took him 803 days' worth of orbiting to do it. See: Cule M. The Future: Time Travel. Quite Interesting 2008-04-25. http://old.qi.com/talk/viewtopic.php?t=11529