I compared 2021b with 2021a. The result is following. I don't understand the meaning for line 3-5,20-22 of 2021b result. Is it correct ? *** tzdb-2021b $ ./zdump -v Pacific/Honolulu Pacific/Honolulu -9223372036854775808 = NULL 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 Pacific/Honolulu Mon Jan 13 22:31:25 1896 UT = Mon Jan 13 11:59:59 1896 LMT isdst=0 gmtoff=-37886 Pacific/Honolulu Mon Jan 13 22:31:26 1896 UT = Mon Jan 13 12:01:26 1896 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Apr 30 12:29:59 1933 UT = Sun Apr 30 01:59:59 1933 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Apr 30 12:30:00 1933 UT = Sun Apr 30 03:00:00 1933 HDT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun May 21 21:29:59 1933 UT = Sun May 21 11:59:59 1933 HDT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun May 21 21:30:00 1933 UT = Sun May 21 11:00:00 1933 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Mon Feb 9 12:29:59 1942 UT = Mon Feb 9 01:59:59 1942 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Mon Feb 9 12:30:00 1942 UT = Mon Feb 9 03:00:00 1942 HWT isdst=1 gmtoff=-34200 Pacific/Honolulu Tue Aug 14 22:59:59 1945 UT = Tue Aug 14 13:29:59 1945 HWT isdst=1 gmtoff=-34200 Pacific/Honolulu Tue Aug 14 23:00:00 1945 UT = Tue Aug 14 13:30:00 1945 HPT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun Sep 30 11:29:59 1945 UT = Sun Sep 30 01:59:59 1945 HPT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun Sep 30 11:30:00 1945 UT = Sun Sep 30 01:00:00 1945 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Jun 8 12:29:59 1947 UT = Sun Jun 8 01:59:59 1947 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Jun 8 12:30:00 1947 UT = Sun Jun 8 02:30:00 1947 HST isdst=0 gmtoff=-36000 Pacific/Honolulu Wed Dec 31 23:59:59 2147485547 UT = Wed Dec 31 13:59:59 2147485547 HST isdst=0 gmtoff=-36000 Pacific/Honolulu 67768036191676800 = Wed Dec 31 14:00:00 2147485547 HST isdst=0 gmtoff=-36000 Pacific/Honolulu 67768036191712799 = Wed Dec 31 23:59:59 2147485547 HST isdst=0 gmtoff=-36000 Pacific/Honolulu 67768036191712800 = NULL Pacific/Honolulu 9223372036854775807 = NULL *** tzdb-2021a $ ./zdump -v Pacific/Honolulu Pacific/Honolulu -9223372036854775808 = NULL Pacific/Honolulu -9223372036854689408 = NULL Pacific/Honolulu Mon Jan 13 22:31:25 1896 UT = Mon Jan 13 11:59:59 1896 LMT isdst=0 gmtoff=-37886 Pacific/Honolulu Mon Jan 13 22:31:26 1896 UT = Mon Jan 13 12:01:26 1896 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Apr 30 12:29:59 1933 UT = Sun Apr 30 01:59:59 1933 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Apr 30 12:30:00 1933 UT = Sun Apr 30 03:00:00 1933 HDT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun May 21 21:29:59 1933 UT = Sun May 21 11:59:59 1933 HDT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun May 21 21:30:00 1933 UT = Sun May 21 11:00:00 1933 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Mon Feb 9 12:29:59 1942 UT = Mon Feb 9 01:59:59 1942 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Mon Feb 9 12:30:00 1942 UT = Mon Feb 9 03:00:00 1942 HWT isdst=1 gmtoff=-34200 Pacific/Honolulu Tue Aug 14 22:59:59 1945 UT = Tue Aug 14 13:29:59 1945 HWT isdst=1 gmtoff=-34200 Pacific/Honolulu Tue Aug 14 23:00:00 1945 UT = Tue Aug 14 13:30:00 1945 HPT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun Sep 30 11:29:59 1945 UT = Sun Sep 30 01:59:59 1945 HPT isdst=1 gmtoff=-34200 Pacific/Honolulu Sun Sep 30 11:30:00 1945 UT = Sun Sep 30 01:00:00 1945 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Jun 8 12:29:59 1947 UT = Sun Jun 8 01:59:59 1947 HST isdst=0 gmtoff=-37800 Pacific/Honolulu Sun Jun 8 12:30:00 1947 UT = Sun Jun 8 02:30:00 1947 HST isdst=0 gmtoff=-36000 Pacific/Honolulu 9223372036854689407 = NULL Pacific/Honolulu 9223372036854775807 = NULL ---- Toshinari Ohyama