In health care, and therefore healthcare standards, we do need to record the time that things happen or should happen. So recording time matters. Leap seconds are a source of problems for recording specific times and time intervals.
The leap second problem is hard because everything you learned in school about time is wrong. It's not wrong in the sense that it causes you to make mistakes. It's wrong in the same way that general relativity makes high school physics wrong, or quantum mechanics makes physics and chemistry wrong. The actual details of how time measurement works are not at all like what you learned. It's worse, because it's not like several hundred years of law and tradition have established. So not only is your elementary school education wrong. The laws and regulations are wrong. This little difference sometimes even matters.
But first, the unlearning of elementary school "facts":
- The earth does not rotate in 86400 seconds.
- A minute has either 59, 60, or 61 seconds.
- The earth does not rotate at a steady speed.
Some people "know" this, and point to tidal slowing of the earth's rotation. It's true, that is an effect. But there are many other astronomical torques that change the earth's rotation. Continental drift also changes the rotation speed. As India moves north, the earth spins faster. As Australia moves north, the earth spins slower. The earthquake that caused the Indian Ocean tsunamis also shifted some mountain ranges, changing the length of the day by about 2.5 milliseconds. The Indian monsoon brings rain and snow north to the Himalayas, making the earth spin faster. Then it flows back, making the earth spin slower. (I worked with some monsoon researchers who were using earth rotation records to estimate the historical monsoon statistics.)
This all became more apparent and began to matter about 1950. That's when atomic clocks became available to scientists, and they started using atomic time references instead of astronomical references. Before then, there was a recognition of a few of the variations, but the available accuracy was limited. People accepted that there was a standard second, the day had 86400 seconds, and there were annually published astronomical tables with the fine tuning corrections.
Eventually (mid 1960's) scientists established the UT* series of time references. The UTC reference replaced the old GMT time. GMT did not attempt to keep sunrise, sunset, midnight, etc. properly located on a regular basis. The "C" in UTC is for coordinated. UTC is coordinated with the earth's rotation so that astronomical events like sunrise and sunset remain within 1 second of their proper time. This is done by introducing leap seconds every year or two. UTC replaced GMT in many legal and regulatory settings. UTC also makes a variety of terrestrial functions like navigation easier.
Most of the world ignored all this. Most of the world did not have clocks accurate enough to notice a one second mismatch. Leap seconds only mattered to the specialist.
Then, atomic clocks kept getting cheaper. Radio synchronized clocks got cheaper. Satellite time signal receivers got cheaper. Internet NTP service got cheaper. Accurate computer clocks got cheaper. When I first needed accurate time it cost about $10K for a clock receiver, and that is before inflation compensation. Now, equally accurate time is free as part of Internet service.
This means that now we have to face the reality of everyone having accurate time. For most people, leap seconds are a pain in the neck. Back in 2003 US proposed eliminating the leap second to the ITU (the standards body responsible for time standards). It lost. There are good uses for leap seconds, and the majority felt that those users should not be disturbed. The computer users who found leap seconds inconvenient should fix their software. The US has not given up, and the world attitudes are shifting. Perhaps leap seconds will be gone by 2020. But we must deal with the interim.
Next: What is the state of standards regarding time, and what is the general state of implementations of those standards.