[time-nuts] Why not TAI?

[mike cook]

Le 11/08/2011 08:57, Attila Kinali a écrit :
> On Wed, 10 Aug 2011 16:35:11 +0200
> cook michael<michael.cook at sfr.fr>  wrote:
>
>>> If TAI is a paper clock, what else should be used if a strictly monotone
>>> time scale is needed?
>> Do you have any specific application in mind?
>> If you need an SI seconds rated scale, then you need something based on
>> TAI. GPS time has a TAI second rate and is monotonic. But of course you
>> would need a GPS receiver to access it.
> I don't have a specific application in mind. Just a general question
> on what should be used. But lets say i want to have a monotonic clock
> for a computer system to timestamp events precisely and unambigously.
>
> Yes, using GPS time (with or without going back to TAI) would be
> a probable solution.
>
> Are there any other time scales available that would fit that need?
>
> 			Attila Kinali
>
Well, there is :

TT, Terrestrial Time, which is uniform (interval SI second), monotonic ; 
with an epoc of
00h 00m 00s 1 Jan 1977 TAI with a constant offset such that [TT] = [TAI] 
- 32.184s .

Or more exotic:

ET, Ephemeris Time, which is uniform and monotonic with a non SI second 
of 1/31566925,9747 of the tropical year of 1900.

Julien Date is another , using SI second, but a numeric day label with 
an epoc of initial epoc defined as (UT) at midday on Monday Jan 1 4713 
BC  in the Julian calendar. It is measured in days and fractions with 
precision of about a millisecond and being numeric is  so is easy to do 
calculations on.
MJD , Modified Julien Date is the above -2400000,5 to keep the numbers 
down. This was recognised as a time scale by the IUT.  I think it is now 
deprecated but is in common use.

There are probably others.