Google is offering time servers that will help you get over the upcoming leap-second hump. Instead of having a day with 61 seconds in it, their clock will run 0.0014% slower across a twenty-hour interval with the moment of the leap second in the middle. At the end of that interval, your clock will be correctly in sync with UTC again. <http://www.theregister.co.uk/2016/12/02/google_public_ntp_servers/>