What should medicine do about leap seconds? (First thoughts)

Previously:

Leap Seconds
State of the Standards
What Matters When measuring
The UNIX-NTP real world compromise
What about SNTP (e.g., Windows)
What's wrong with the UNIX-NTP compromise?
What else is wrong with the compromise

Wishful thinking:  Just switch to TAI.  (TAI is the basic atomic time used by UTC, but without any of the leap seconds.)   Medicine doesn't care if earth-astronomical times drift slowly away.  Details about sunrise and sunset don't matter.  TAI is simple, well behaved, and entirely appropriate to medicine.

Unpleasant reality:  Pushing all of our ISO/ITU representatives to support the removal of leap seconds is more likely to succeed.  It is easier than dealing with the constant education and explanation issues that would arise if medicine were to just abandon UTC in favor of TAI.  Two industries have succeeded in ignoring UTC.

• Telecommunications (both landline and cellular).  These systems depend upon extremely precise timings among equipment scatter across continents.  Their timing demands are much stricter than anything in medicine.  Introducing leap seconds would have cost a huge amount of engineering, reduced reliability, increased cost, and served no purpose.  So telecommunications networks all use variations on TAI.  They are mostly of the form TAI+n seconds.  Telecommunications has extremely little need to share data with the rest of the world, so they just convert to approximately UTC when necessary for things like billing records.  Many such records are only accurate to the minute, so the conversion is often just roundoff error.
• Global Positioning Satellites (GPS).  Like telecommunications, these have extremely precise timing requirements that pushed the state of the art of atomic clocks.  GPS time is also TAI+n seconds.  Sunrise, sunset, etc.  are irrelevant to GPS.   GPS time is an almost closed system.  If you want to get GPS time, some receivers will provide it.  (Be careful with this.  Many of the low cost receivers have rather high phase errors and jitter.  They were designed for accurate positioning, not accurate timing.)

Medicine has almost constant interactions with non-medical systems at the administrative level.  So while it could act like telecommunications, there would be a lot of potential confusion and explanation needed.

If we can get leap seconds removed from UTC it would eliminate all this explanation and solve our forward looking problem.  Maybe the 2012 efforts will be successful.  The 2003 effort by the US was not sufficiently persuasive.   Increasing numbers of people are understanding that how much more this is beyond a simple "fix your software", and by 2012 we may be willing to watch sunrise and sunset slowly drift in the clock rather than suffer with extensive software design problems.

Unfortunately, standards are only part of the solution.  We have an unpleasant and inescapable legacy problem.  What should we do with all the existing records.  Some are administrative scope, some are operating system scope, many are poorly documented scope, many have timing errors.  This is all part of the growing petabytes of medical record.

Until leap seconds are removed, this will continue to grow at the rate of petabytes per year.

I believe that some variation on the UNIX-NTP compromise will be needed when dealing with all these records.  At least properly implemented DICOM objects provide a UID that identifies their time synchronization source.  This can be used to automate some of the grunt work of correlating and correcting records when necessary.

Next: Medical standards and leap seconds (aka Navigators vs Doctors)

Comments

[Steve Allen]

The BIPM unequivocally "owns" TAI, and they give several reasons why TAI is not appropriate as the base time scale.

Even if the underlying broadcast/internet/POSIX time scale abandons leaps, it is not guaranteed that all systems will have their chronometers set correctly. The navigators of ships knew this 200 years ago, and their solution is still valid -- use your own chronometer and keep a log of how far off it is from "true" time.

[fairhavenhorn]

As I said, "wishful thinking". The reality is more practical but more work.

Thinking about navigator and why medicine is a different and harder problem. But RSNA gets in the way.