Zoneinfo file format
 

Hi All.

I am trying to figure out how to make the zoneinfo files smaller by filtering out historical data (due to TIGHT space on an older embedded system). Currently using "northamerica" file as example.

For zones like America/New_York it seems I need to do something like this:

# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER
Rule NYC 1920 only - Mar lastSun 2:00 1:00 D
Rule NYC 1920 only - Oct lastSun 2:00 0 S
Rule NYC 1921 1966 - Apr lastSun 2:00 1:00 D
Rule NYC 1921 1954 - Sep lastSun 2:00 0 S
Rule NYC 1955 1966 - Oct lastSun 2:00 0 S

# Zone NAME GMTOFF RULES FORMAT [UNTIL]
Zone America/New_York -4:56:02 - LMT 1883 Nov 18 12:03:58
-5:00 US E%sT 1920
-5:00 NYC E%sT 1942
-5:00 US E%sT 1946
-5:00 NYC E%sT 1967
-5:00 US E%sT

Would change to:

# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER
# no rules

# Zone NAME GMTOFF RULES FORMAT [UNTIL]
Zone America/New_York -4:56:02 - LMT 1883 Nov 18 12:03:58
-5:00 US E%sT

Question: I don't understand what -4:56:02 is all about and whether it can be "simplified" further. Can I just replace the zone info with "Zone America/New_York -5:00 US E%sT"?

I'm having trouble with Guatemala (for example):

# 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
Rule Nic 2005 only - Apr 10 0:00 1:00 D
Rule Nic 2005 only - Oct Sun>=1 0:00 0 S
Rule Nic 2006 only - Apr 30 2:00 1:00 D
Rule Nic 2006 only - Oct Sun>=1 1:00 0 S
# Zone NAME GMTOFF RULES FORMAT [UNTIL]
Zone America/Managua -5:45:08 - LMT 1890
-5:45:12 - MMT 1934 Jun 23 # Managua Mean Time?
-6:00 - CST 1973 May
-5:00 - EST 1975 Feb 16
-6:00 Nic C%sT 1992 Jan 1 4:00
-5:00 - EST 1992 Sep 24
-6:00 - CST 1993
-5:00 - EST 1997
-6:00 Nic C%sT

Question: How does this work? Nic rule is not specified for 2007+ ...yet last line is "-6:00 Nic C%sT" which, I believe, implies that Nic rule is in use currently. ... Am I missing something here or is this a bug in the northamerica zoneinfo source file?

If somebody could point me to an appropriate m it would be greatly appreciated =)

Thanks in advance for any info / suggestions.

-Pavel