[LEAPSECS] Bulletin C and all that

[Warner Losh]

> On Jan 25, 2015, at 6:15 PM, G Ashton <ashtongj at comcast.net> wrote:
> 
> Rob Seaman also wrote:
>> Leap seconds are introduced at midnight UTC, not when TAI modulo 86400
> equals zero.
> 
> I would think that midnight UTC is the instant when the UTC time becomes
> 00:00:00. I would call the introduced second the one that began at 11:59:60
> and ended one second later at 00:00:00.

The second half of what Rob said is correct for at least some tens of thousands
of years.  :). Leap seconds are introduced just before midnight UTC, and are
properly part of the last day of the month, not the first day of the following month.

Warner