# TAI zone?

Ian Abbott abbotti at mev.co.uk
Fri Jul 1 13:37:41 UTC 2011

On 01/07/11 12:59, Clive D.W. Feather wrote:
> Now imagine a second clock. This also ticks once per second. Right now it's
> 34 seconds behind the TAI clock, so it is saying 2011-07-01 11:28:11.
> This clock has 60 minutes to the hour, 24 hours to the day, 28/29/30/31 days
> to the month, and 12 months to the year, but while it usually has 60
> seconds to the minute, it sometimes has 59 or 61 - these minutes are always
> the last minute of a month. So at the end of this year it could tick any of:
>
>     2011-12-31 23:59:56    2011-12-31 23:59:56    2011-12-31 23:59:56
>     2011-12-31 23:59:57    2011-12-31 23:59:57    2011-12-31 23:59:57
>     2011-12-31 23:59:58    2011-12-31 23:59:58    2011-12-31 23:59:58
>     2012-01-01 00:00:00    2011-12-31 23:59:59    2011-12-31 23:59:59
>     2012-01-01 00:00:01    2012-01-01 00:00:00    2011-12-31 23:59:60
>     2012-01-01 00:00:02    2012-01-01 00:00:01    2012-01-01 00:00:00
>     2012-01-01 00:00:03    2012-01-01 00:00:02    2012-01-01 00:00:01
>     2012-01-01 00:00:04    2012-01-01 00:00:03    2012-01-01 00:00:02
>
> (and we don't yet know which of them it will be). This is the UTC clock.
> Note that TAI-UTC is always an integer number of seconds.

And even *that* goes horribly wrong after a couple of thousand years or
so when we'd need more than one leap second per month!

--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-