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From: Ed Davies <ls_at_EDAVIES.NILDRAM.CO.UK>

Date: Fri, 13 Jan 2006 11:45:13 +0000

Michael Deckers wrote:

*> I believe I'm now grasping what you mean: the rate of UTC is the same
*

*> as the rate of TAI (since 1972), that is, the derivative
*

*> d( UTC )/d( TAI ) = 1. ...
*

This conversation is making something of a meal of a simple

point. You can treat UTC as a real in either of two ways:

If you don't count the leap seconds then the good news is that

days are all 86 400 seconds long but the bad news is that the

real is undefined during the leap second and there's a

discontinuity (or rather, a surprising continuity in that

at some point it's 23:59:59.999999.... and a whole second and

a tiny bit later it's 00:00:00.0000....).

If you do count the leap seconds then that real is the same

as TAI but the days it's divided up into aren't all 86 400

seconds long.

Sort of like, is it a particle or a wave? :-)

The truth is that UTC only really makes sense as a year,

month, day, hour, minute and second value. Years have 12

months, months have 28, 29, 30 or 31 days, days have 24

hours, hours have 60 minutes, minutes have 59, 60 or 61

seconds.

The use of the 23:59:60 notation is described in ISO 8601.

Is it also specified in TF.460? If so, how do they relate

it to the notion of DTAI?

Ed.

Received on Fri Jan 13 2006 - 03:45:42 PST

Date: Fri, 13 Jan 2006 11:45:13 +0000

Michael Deckers wrote:

This conversation is making something of a meal of a simple

point. You can treat UTC as a real in either of two ways:

If you don't count the leap seconds then the good news is that

days are all 86 400 seconds long but the bad news is that the

real is undefined during the leap second and there's a

discontinuity (or rather, a surprising continuity in that

at some point it's 23:59:59.999999.... and a whole second and

a tiny bit later it's 00:00:00.0000....).

If you do count the leap seconds then that real is the same

as TAI but the days it's divided up into aren't all 86 400

seconds long.

Sort of like, is it a particle or a wave? :-)

The truth is that UTC only really makes sense as a year,

month, day, hour, minute and second value. Years have 12

months, months have 28, 29, 30 or 31 days, days have 24

hours, hours have 60 minutes, minutes have 59, 60 or 61

seconds.

The use of the 23:59:60 notation is described in ISO 8601.

Is it also specified in TF.460? If so, how do they relate

it to the notion of DTAI?

Ed.

Received on Fri Jan 13 2006 - 03:45:42 PST

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