I'm not sure if all the patches are commited as for now, but it still doesn't work for me. First, IDT setting still returns unknown timezone, second, now PHP crashes in:
0x08095bcd in timelib_tzinfo_dtor (tz=0x0) at php5/ext/date/lib/timelib.c:107
107 TIMELIB_TIME_FREE(tz->name);
(gdb) bt
#0 0x08095bcd in timelib_tzinfo_dtor (tz=0x0) at php5/ext/date/lib/timelib.c:107
#1 0x08076f31 in _php_date_tzinfo_dtor (tzinfo=0xa3252a0) at php5/ext/date/php_date.c
if I set 'IDT' timezone. Same if I set 'IST' timezone.
This patch should fix the segfault:
http://mega.ist.utl.pt/~ncpl/php_date_segf.txt
The problem of not recognising your timezones is because currently the code isn't doing any guessing magic (aka guess full name from abbr) when the TZ environment var is set.
Perhaps a timelib_timezone_id_from_abbr() call could be added in the 'if (env && *env)' section.
Nuno