[Pool] Leap second is coming

Miroslav Lichvar mlichvar at redhat.com
Mon Apr 20 09:11:27 UTC 2015

> On 18-04-15 20:44, Hal Murray wrote:
> > The leap insert/delete apply to the end of the current day.
> If I understand the spec (section 7.3 of RFC5905) correctly, the leap indicator
> refers to the last minute of the *last day* of the current month.
>   "LI Leap Indicator (leap): 2-bit integer warning of an impending leap
>    second to be inserted or deleted in the last minute of the current
>    month with values defined in Figure 9."

Actually, it's more confusing. Below that paragraph is a table which

 | 1     | last minute of the day has 61 seconds  |
 | 2     | last minute of the day has 59 seconds  |

In RFC 1305 and RFC 4330 it's always last minute of day. So I think
it's supposed to be day and not month. There are NTP implementations
that don't check what day it is and set the kernel flag at any time.
They would be broken if it was announced sooner than last day.

In older ntp versions (pre 4.2.6) the leap bits were announced in
whole month and not the last day, but in newer versions it's only the
last day.

It would be nice to have an RFC erratum for that to avoid confusion.

Miroslav Lichvar

More information about the pool mailing list