On Mon, 8 Jan 2007, Zefram wrote: > Possibly TT could also be used in some form, for interval calculations > in the pre-caesium age.
In that case you'd need a model (probably involving rubber seconds) of the TT<->UT translation. It doesn't seem worth doing to me because of the small number of applications that care about that level of precision that far in the past. The main requirement for a proleptic timescale is that it is useful for most practical purposes. Therefore it should not be excessively complicated, such as requiring a substantially different implementation of time in the past to time in the present. What we actually did in the past was make a smooth(ish) transition from universal time to atomic time, so it would seem reasonable to implement (a simplified version of) that in our systems. In practice this means saying that we couldn't tell the difference between universal time and uniform time before a certain date, which we model as a leap second offset of zero. Tony. -- f.a.n.finch <[EMAIL PROTECTED]> http://dotat.at/ BAILEY: SOUTHWEST 5 TO 7 BECOMING VARIABLE 4. ROUGH OR VERY ROUGH. SHOWERS, RAIN LATER. MODERATE OR GOOD.