<<I use TZ = NZST-12NZDT but that seems to put the time one hour out
during daylight saving time.>>


This might be an RC issue; it could be more than a coincidence that the NZ
time zone in TZTAB is the only one that uses a "-13" value.

In fact, the TZTAB entry for NZ looks odd even ignoring the "-13" value:

# New Zealand Standard Time, New Zealand Daylight Time
#
NZST-12NZDT
0 3 25-31 10 1985-1988 0   NZDT-13
0 3 8     10 1989      0-6 NZDT-13
0 3 1-7   10 1990-1999 0   NZDT-13
0 1 1-7   3  1985-1989 0   NZST-12
0 1 15-21 3  1990-2038 0   NZST-12

Has NZ decided to discontinue the switch to DST after 1999? With this TZTAB
entry, there won't be an automatic switch to DST in or after 2000.

Steve