Super Volatile

Very large-scale distributed systems, like ours, demand that time be well-synchronized and expect that time always moves forwards. Computers traditionally accommodate leap seconds by setting their clock backwards by one second at the very end of the day. But this “repeated” second can be a problem. For example, what happens to write operations that happen during that second? Does email that comes in during that second get stored correctly? What about all the unforeseen problems that may come up with the massive number of systems and servers that we run? Our systems are engineered for data integrity, and some will refuse to work if their time is sufficiently “wrong.” We saw some of our clustered systems stop accepting work on a small scale during the leap second in 2005, and while it didn’t affect the site or any of our data, we wanted to fix such issues once and for all.

Since most of us have already sold our privacy to Google company, it's at least some consolation to know that they care even about such seemingly minor issues like leap seconds.