On Dec 25, 2006, at 9:56 PM, M. Warner Losh wrote:
Also, things in TAI time don't care either. 1 day, 1 year, 100 years don't matter to TAI. Periodic things that happen at a given time of day (UTC) are the only things that do care.
Well, champions of pure TAI consciousness might assert that all Universal Time is aperiodic :–) Whether any application "cares" isn't just a function of the timescale, but of the application. It is precisely the impossibility of mapping time-of-day to inflexible SI seconds that makes TAI (or a putative leapsecond-less UTC) a poor choice for conveying fractional representations of calendar dates. Any attempt to produce a better compromise civil time scale than the current UTC should start by characterizing the many civilian timekeeping applications and by valuing the various economic (and scientific, cultural, legal, historical) trade-offs. It might be an interesting exercise to design a separate API for representing and conveying interval time from time-of-day. Two types of time, two APIs. Then design the minimal set of conversion routines after understanding under what circumstances such conversions are necessary. Even in the easy case of strictly linear unit conversions, such as Celsius to Fahrenheit or milliliters to fluid ounces, users only have to convert back-and-forth under relatively rare circumstances. One might also point out that even in these cases multiple standards persist. For some units, e.g., parsecs and light-years, there is some demonstrable scientific reason for using two sets of units. For other units, for example, centimeters versus inches, there is no reason beyond cultural and economic hysteresis. For timekeeping, however, interval time and time-of-day are simply two entirely separate concepts. If virtually every ruler in America conveys both inches and centimeters, why should our clocks (time-of-day) and our stopwatches (interval timers) be force fit to a single pseudo-standard? Rob
