zdump returns incorrect transitions for Africa/Casablanca and Africa/El_Aaiun

[Philip Ross]

Ubuntu 16.04 LTS amd64
libc-bin 2.23-0ubuntu3
tzdata 2016d-0ubuntu0.16.04

The Africa/Casablanca and Africa/El_Aaiun time zones in the 2016d-0ubuntu0.16.04 tzdata package have transitions from daylight savings to standard time at 02:00 UTC on 2037-10-04 (see https://github.com/eggert/tz/blob/2016d/africa#L892).

The time zone files (/usr/share/zoneinfo/Africa/Casablanca and /usr/share/zoneinfo/Africa/El_Aaiun) both contain the correct transition time (Unix timestamp 0x7f72de20) in the 32-bit and 64-bit sections:

$ hd -s 0x1b8 -n 4 /usr/share/zoneinfo/Africa/Casablanca
000001b8 7f 72 de 20 |.r. |
000001bc

$ hd -s 0x59d -n 8 /usr/share/zoneinfo/Africa/Casablanca
0000059d 00 00 00 00 7f 72 de 20 |.....r. |
000005a5

$ hd -s 0x18c -n 4 /usr/share/zoneinfo/Africa/El_Aaiun
0000018c 7f 72 de 20 |.r. |
00000190

$ hd -s 0x506 -n 8 /usr/share/zoneinfo/Africa/El_Aaiun
00000506 00 00 00 00 7f 72 de 20 |.....r. |
0000050e

However zdump (from libc-bin 2.23-0ubuntu3) incorrectly shows that the transitions for both time zones occur on 2037-10-25 instead of 2037-10-04:

$ zdump -v -c 2037,2038 /usr/share/zoneinfo/Africa/Casablanca | grep Oct
/usr/share/zoneinfo/Africa/Casablanca Sun Oct 25 01:59:59 2037 UT = Sun Oct 25 02:59:59 2037 WEST isdst=1 gmtoff=3600
/usr/share/zoneinfo/Africa/Casablanca Sun Oct 25 02:00:00 2037 UT = Sun Oct 25 02:00:00 2037 WET isdst=0 gmtoff=0

$ zdump -v -c 2037,2038 /usr/share/zoneinfo/Africa/El_Aaiun | grep Oct
/usr/share/zoneinfo/Africa/El_Aaiun Sun Oct 25 01:59:59 2037 UT = Sun Oct 25 02:59:59 2037 WEST isdst=1 gmtoff=3600
/usr/share/zoneinfo/Africa/El_Aaiun Sun Oct 25 02:00:00 2037 UT = Sun Oct 25 02:00:00 2037 WET isdst=0 gmtoff=0

The copy of zdump.c released with glibc 2.23 is identical to zdump.c in the tzcode2015g release from the IANA Timezone Database (https://www.iana.org/time-zones/repository/releases/tzcode2015g.tar.gz).

I have compiled the IANA Timezone Database 2015g version of zdump with the default options and it produces the correct results for the Ubuntu-distributed Africa/Casablanca and Africa/El_Aaiun time zone files:

$ ~/tz/2015g/zdump --version
zdump (tzcode) 2015g

$ ~/tz/2015g/zdump -v -c 2037,2038 /usr/share/zoneinfo/Africa/Casablanca | grep Oct
/usr/share/zoneinfo/Africa/Casablanca Sun Oct 4 01:59:59 2037 UT = Sun Oct 4 02:59:59 2037 WEST isdst=1 gmtoff=3600
/usr/share/zoneinfo/Africa/Casablanca Sun Oct 4 02:00:00 2037 UT = Sun Oct 4 02:00:00 2037 WET isdst=0 gmtoff=0

$ ~/tz/2015g/zdump -v -c 2037,2038 /usr/share/zoneinfo/Africa/El_Aaiun | grep Oct
/usr/share/zoneinfo/Africa/El_Aaiun Sun Oct 4 01:59:59 2037 UT = Sun Oct 4 02:59:59 2037 WEST isdst=1 gmtoff=3600
/usr/share/zoneinfo/Africa/El_Aaiun Sun Oct 4 02:00:00 2037 UT = Sun Oct 4 02:00:00 2037 WET isdst=0 gmtoff=0