# [time-nuts] Why not TAI?

Bob Camp lists at rtty.us
Wed Aug 10 17:03:13 UTC 2011

```Hi

If you have a time source to work with, generating a different time scale is
just a math problem. In most cases it's not a very complex one (subtract 19
seconds and move on). If you don't have a time source, then generating any
time scale will be a challenge.

Given the low cost of computing gizmos these days, doing the math to come up
with what ever you want is not going to be all that hard or expensive.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of cook michael
Sent: Wednesday, August 10, 2011 10:35 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Why not TAI?

Le 10/08/2011 12:55, Attila Kinali a écrit :
>
> 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.

> And what makes UTC different from TAI to be a "real clock", as UTC is
> derived from TAI by adding leap seconds?

I don't think TAI is any less real than UTC. UTC just happens to be
the international transmitted time scale. TAI is not generally
available, though both GPS time, and UTC have the same rate.

> Would a reverse definition of TAI (or rather TAI' ) by using UTC without
the
> leap seconds be a good enough approximation?

Well, UTC doesn't exist without leap seconds by definition, but if you
only have UTC available to be able to track TAI , then you can recover
the  TAI  scale by deducting leap seconds.

> I'm quite sure i'm not the first one asking this question, but i couldn't
> find an answer, neither with google nor in the time-nuts archives.
>
> 			Attila Kinali

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