[tz] zdump bug in Asia/Singapore

[Paul Eggert]

Tim Parenti wrote:
>   most users would expect to find such a transition in the
> year you call N+1, since that's when the actual onset of the transition occurs.

I'm not so sure.  In everyday English there's not a general agreement 
whether midnight falls at the end of day N, or between day N and day 
N+1, or at the start of day N+1.  This ambiguity is why so many laws 
take effect one minute after midnight.  See, for example:

www.nist.gov/pml/div688/times.cfm#midnight

It's plausible for zdump to consider a transition from 23:59:59 (which 
is inarguably the previous day) to midnight (which is ambiguous) to be 
in the previous day.  It's also plausible for zdump to consider it to be 
in the next day.  Whatever.  It doesn't really matter, so long as zdump 
is consistent about it.