[LEAPSECS] Time Synchronization in Financial markets

[Martin Burnicki]

John Sauter wrote:
> I took the lack of mention of leap seconds to mean that leap seconds
> ere not a problem.  The output of the NISTDC units is an astonishingly
>  accurate 1 pulse per second.  That feeds NTP, which handles leap
> seconds using a table.  As long as the table is kept up to date,
> everyone agrees on each second's name.

I don't think this is true.

On *ix systems ntpd uses the leap second table *only* as one possible
source to determine that a leap second has been scheduled. As a
consequence a leap second announcement flag is included in the replies
to the NTP clients, and is also passed to the OS kernel.

It's the kernel who actually inserts the leap second by stepping the
binary system time back, and as already mentioned in my other reply most
library functions are unable to distinguish the leap second from the
"normal" second, and thus yield the same time 23:59:59 twice.

This is similar to the end of DST, where a particular hour is repeated,
and you don't know if you refer to the first or second occurrence if you
don't take the DST status into account.

Martin