Why clocks could change in 2029.
Earth May Skip Time by One Second
Earth is spinning faster than it used to and now world
timekeepers are considering skipping time – by one second.
Clocks may have to skip a second – called a “negative leap second” – when 2029 rolls around.
This is an unprecedented situation and a big deal,” one geophysicist explained. “It’s not a huge change in the Earth’s rotation that’s going to lead to some catastrophe or anything, but it is something notable. It’s yet another indication that we’re in a very unusual time.” 
Scientists believe melting polar caps, caused by climate change, is playing a role in the planet’s rotation.