[tz] Question about leap seconds

[random832 at fastmail.us]

On Wed, Sep 11, 2013, at 11:58, Ian Abbott wrote:
> A leap second would be inserted at 23:59:60 UTC, so I'm not sure it's 
> possible to have a DST transition at the start of a leap second, but you 
> could get a DST transition at the end of a leap second.

Otherwise known as the start of the next second after, and i'm pretty
sure transitions are defined in the file by the second that starts at
the time of the transition.