Hi Paul, I rebased to the latest, since your patch was already merged so I used it to test a bit. I am a bit confused about the result, maybe you can explain to me: ### Rule from africa: # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone Africa/Abidjan -0:16:08 - LMT 1912 0:00 - GMT ### Compiled data using @220924800 should correspond to 1977 for tz in etcetera southamerica northamerica europe africa antarctica \ asia australasia backward systemv factory; do ./zic -L /dev/null -d $ZONEINFO -r @220924800 -y "sh yearistype.sh" ${tz} done ./zdump -v $ZONEINFO/Africa/Abidjan ### Got the following output: /home/christwo/dists/tz/test_zic_github/Africa/Abidjan -9223372036854775808 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan -9223372036854689408 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan Fri Dec 31 23:59:59 1976 UT = Fri Dec 31 23:43:51 1976 LMT isdst=0 gmtoff=-968 /home/christwo/dists/tz/test_zic_github/Africa/Abidjan Sat Jan 1 00:00:00 1977 UT = Sat Jan 1 00:00:00 1977 GMT isdst=0 gmtoff=0 /home/christwo/dists/tz/test_zic_github/Africa/Abidjan 9223372036854689407 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan 9223372036854775807 = NULL ### Compiled data using @441763200 should correspond to 1984 for tz in etcetera southamerica northamerica europe africa antarctica \ asia australasia backward systemv factory; do ./zic -L /dev/null -d $ZONEINFO -r @441763200 -y "sh yearistype.sh" ${tz} done ./zdump -v $ZONEINFO/Africa/Abidjan ### Got the following output: /home/christwo/dists/tz/test_zic_github/Africa/Abidjan -9223372036854775808 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan -9223372036854689408 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan Sat Dec 31 23:59:59 1983 UT = Sat Dec 31 23:43:51 1983 LMT isdst=0 gmtoff=-968 /home/christwo/dists/tz/test_zic_github/Africa/Abidjan Sun Jan 1 00:00:00 1984 UT = Sun Jan 1 00:00:00 1984 GMT isdst=0 gmtoff=0 /home/christwo/dists/tz/test_zic_github/Africa/Abidjan 9223372036854689407 = NULL /home/christwo/dists/tz/test_zic_github/Africa/Abidjan 9223372036854775807 = NULL Is it correct that the switch between LMT to GMT is set to the specified start of the time range? I also tried with the time range "-r @220924800/@441763200" then I encountered some segmentation fault error prints when I ran that. I haven't investigated any further on that. BR, Christopher Wong ________________________________________ From: Paul Eggert <eggert@cs.ucla.edu> Sent: Saturday, March 9, 2019 06:34 To: Christopher Wong; Scott Nelson Cc: Time Zone Mailing List Subject: Re: [tz] [PROPOSED] zic option for including data from a certain year onward Thanks for suggesting that. I looked into the issue, and it can be a trickier to truncate the output because truncation also affects things like the default time type and the TZ string, and truncation might affect the 32-bit data (which is already truncated) differently from the 64-bit data. I wrote a different implementation, which supports truncating newer timestamps as well, as per Internet RFC 8536. Please give the attached proposed patch a try.