[LEAPSECS] BBC radio Crowd Science

GERRY ASHTON ashtongj at comcast.net
Wed Feb 1 06:47:03 EST 2017

> On February 1, 2017 at 3:24 AM Zefram <zefram at fysh.org> wrote in part:
> The maths isn't done in the irregular radix.  For the purposes of
> expressions such as "TAI - UTC" that require a UTC time to be reduced to
> a scalar value, that scalar is derived using the regular radix values.
> This means that, yes, 2016-12-31T23:59:60 and 2017-01-01T00:00:00 have the
> same scalar value.  The jump of TAI-UTC up by 1 s causes the repetition
> of the preceding 1 s worth of UTC scalar values.

I guess "reduced to scalar value" means applying a procedure such as:

Parse time stamp into Y, M, D, H, M, S, with the obvious meanings.

A = seconds from 1 January 1 BC to but not including 1 January Y, excluding leap seconds
B = seconds from 1 January Y to 1 M Y, excluding leap seconds
SV = A + B + (D-1)*86400 + H*3600 + M*60 + S

Such an SV would indeed have the same value for 2016-12-31T23:59:60 and 2017-01-01T00:00:00.
But during the UTC seconds beginning at 2016-12-31T23:59:60 and 2017-01-01T00:00:00 different events happened. The molecules that flowed through my heart during the first of these seconds were different from the ones that flowed during the second of these seconds. So SV seems inadmissable in any system that is expected to accurately label events during the leap seconds.

Gerard Ashton

More information about the LEAPSECS mailing list