[tz] something wrong with 2021b zdump

Paul Eggert eggert at cs.ucla.edu
Wed Sep 29 09:15:24 UTC 2021

On 9/28/21 5:38 PM, 大山俊成 via tz wrote:
> I don't understand the meaning for line 3-5,20-22 of 2021b result.  Is it correct ?

I think it's correct, unless you're seeing something I don't.

2021b zdump changed as noted in NEWS; look for "zdump -v now outputs 
timestamps at boundaries of what localtime and gmtime can represent". 
You can see the full documentation and source-code change here:


zdump -v's new output differs from (and is intended to be more useful 
than) the old zdump -v output. For example, where the old zdump -v would 
have output the following, which doesn't correspond to any transition at 

   Pacific/Honolulu  -9223372036854689408 = NULL

the new zdump -v outputs the following for the two transitions at 
(-67768040609740801) → (Thu Jan  1 00:00:00 -2147481748 UT), when gmtime 
starts succeeding, and at (Thu Jan  1 10:31:25 -2147481748 UT) → (Thu 
Jan  1 10:31:26 -2147481748 UT), when localtime starts succeeding:

   Pacific/Honolulu  -67768040609740801 = NULL
   Pacific/Honolulu  Thu Jan  1 00:00:00 -2147481748 UT = NULL
   Pacific/Honolulu  Thu Jan  1 10:31:25 -2147481748 UT = NULL
   Pacific/Honolulu  Thu Jan  1 10:31:26 -2147481748 UT = Thu Jan  1 
00:00:00 -2147481748 LMT isdst=0 gmtoff=-37886

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