well im not sure how these clocks handle the leap second, or if they even display it. these "atomic" clocks that some people have in their homes arent really atomic, they simply receive a radio signal from NIST/USNO's atomic clock in Colorado, and thats how the "atomic" clock in your home stays synced.

So clocks' seconds display goes from 0-59 then back to 0 after incrementing the minute field, and Ive thought of 4 different ways they could be handled:

1) we actually see the rare 60 displayed in the seconds field

2) we see 59 for 2 seconds

3) 59 for one second followed by 00 for 2 seconds

now either of these 3 implies that that the clocks radios is always receiving, which would use lots of power and would quickly drain batteries of these types of clocks that use batteries. so this leads me to believe that #4 is what will prob happen.

4) the clock does as usual and just goes back to 0 after 1 second at being at 59.  so the clock stays 1 second off until whenever the next time the clock's radio activates and checks the time.

so if either of 1 - 3 happens, we know your clock is always synced.

Look for 6:59:60 CDT tonight

they plan to  adapt the second while you sleep. since every single person that uses  time needs to sleep .  well their you go ......  one second   really.

Most likely my watch will update 1 second sometime afterwards.  I'll never notice.

I'm pretty sure watches and clocks only update themselves once every 6, 12, or 24 hours, and even then the sync message takes 60 seconds to transmit, so I seriously doubt anyone would be able to see the change real-time.

If you have an honest WWV decoder, it will show the leap second flag.

Nice high-end atomic clocks will show it as well.

Mine will correct themselves with the connect to WWVB during the night.

Most atomic clocks only set themselves once a day and thats at night. The frequencies the time broadcast is on requires a long antenna. Since you can't cram a long antenna in the atomic clocks they make due with what they have. The signal propagates better at night due to atmospheric changes. And people go to sleep so RF noisy devices are turned off. Reception gets better so they only turn on their receiver at that point.

I have several of these atomic clocks & it's not uncommon for there to be a 10-15 second difference between them. Sometimes they wont be able to update for several days at a time.

These "atomic clocks" just get the VLF radio signal from WWVB, which transmits on 60Khz from Fort Collins, CO.

You'll just see a one second lurch the next time it fires up the receiver and successfully gets the time from the transmitter. There is no constant correction on these, unless you spend LOTS of money.

Yeah, the wavelength for 60Khz is darn close to 5000 meters, or 3.1 miles long.  You're not going to get much in the way of an efficient antenna on anything you can put on your desk or hang on the wall.  :)

Back when I was doing calibration work, we used the radio rig below, and compared WWVB to a local oscillator.   The antenna was a wirewound T about the size of two jumbo slurpee cups.