[time-nuts] June 30 2015 leap second

Tom Van Baak tvb at LeapSecond.com
Sun Jan 11 09:31:12 EST 2015

> Keep in mind that this system drives you to having pretty bad time for the
> better part of a whole day, on purpose... I realize that when the

Hi Didier,

The google article never claims the smear spans an entire day. I think you may be confusing references to the leap smear with a DIY digital clock someone on the list wanted to build (and they proposed using a slow 86400 second slew).

The google code is "lie(t) = (1.0 - cos(pi * t / w)) / 2.0" and they are wise not to publish the actual window value, w. If it were me I'd make it somewhere between a couple of seconds or couple of minutes but I too would not make it a published or hardcoded constant.

Here's the link again:

Again, I don't know what value they use, or even if they use the same value from one leap second to the next. If any of you have inside contacts with google and can find out let me know, off-list.

Regardless, it should be possible to experimentally determine the smear duration by repeatedly using some google service that returns time-stamps during the day, hours, minutes, or seconds before and after June 30. It would make a nice posting for a time nut, or a research paper for a high school student or undergrad: Experimental Confirmation of Google's Leap Smear Algorithm.


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