[tz] Posix time zone question

[Donald MacQueen]

Hi all,

I am adding time zone support to our multi-platform application and there are
still a few things I cannot figure out.

1) What is the difference between America/Detroit and posix/America/Detroit? The
test cases I have written return what looks like the same DST record for a given
date no matter which one I use. Under what circumstances would I use
posix/America/Detroit?

2) Where is the format of the tz source filesdescribed? Specifically what do
SAVE and Letter/S mean below? I am also interested in what the Link format is.

# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
Rule	Nic	1979	1980	-	Mar	Sun>=16	0:00	1:00	D
Rule	Nic	1979	1980	-	Jun	Mon>=23	0:00	0	S

3) AIX machines use their own wacky format such at TZ=EST5EDT. Is there any
decent mapping to real names?

I have googled my brains out on this and searched the comp.time.tz archives on
gmane with no luck.

Thanks in advance,

Donald