Who thought that a single second could cause such a problem?!?!? Let me begin with the definition of a leap second. A leap second is a single second added to official clocks every now and then to keep clocks based on Earth's rotation matched with extremely accurate atomic clocks. The reason this is needed is due to the fact that Earth's rotation is very slowly slowing down. This requires us to add seconds to the clock every now and then.
The last leap second added to our clocks occurred in 2012 and a total of 25 leap seconds have been added since 1972. Not a lot, but over time it becomes a bigger issue. So what's the problem? Every time a leap second is added, it causes problems with computer software programs not fully capable of easily handling the extra second. In 2012 this caused many major websites to experiences issues. Those issues were fixed, but fixes cost money and in a world increasingly dependent on software, that money adds up.
It's time to add another leap second since we are 1 second ahead of Earth's rotation. There's a debate on whether a leap second should be added this coming June. On one hand, keeping up with Earth's rotation is important. On the other, it's just a second and many argue the technology problems outweigh the differences in clock times.
There's a vote coming up to abolish the leap second (how do I get on that committee!) If the leap second is abolished, the world's clocks will move further and further ahead of Earth's rotation. Again, it's not a lot, but by the year 3015, we'll be 16 minutes ahead of the Earth. If civilization survives for thousands of years, those seconds turn to more minutes and eventually turn to hours. Eventually something must be done as 10 AM will one day represent the middle of the night.