On Tue 05 Dec 2023 at 23:37:31 (+0700), Max Nikulin wrote: > On 05/12/2023 05:14, Pocket wrote: > > For gene.................................................................. > [...] > > zone=EST5EDT > > zoneinfo=/usr/share/zoneinfo > > localtime=/etc/localtime > > timezone=/etc/timezone > > profile=/etc/profile.d > > if [ -e "$zoneinfo"/"$zone" ];then > > ln -sf "$zoneinfo"/"$zone" "$localtime" > > else > > printf "%s\n" "Invalid zone: $zoneinfo/$zone" > > exit 1 > > fi > > printf "%s\n" "$zone" > "$timezone" > > printf "%s\n" "TZ=$zone;export TZ" > "$profile"/timezone.sh > > To set /etc/localtime and /etc/timezone I would recommend the command > that has been repeated several times in this thread: > > dpkg-reconfigure tzdata > > And I would recommend against setting the TZ environment variable > unless it is really necessary. If somebody needs it then it is better > to do it in /etc/environment.d as well. KDE has its own GUI to set > user-specific timezone, but I am unsure if selected value will be > applied in the case of console or ssh login. > > I am surprised that POSIX EST5EDT timezone has irregularities at least > as it is implemented in GNU libc. I believed that it specifies just > standard and summer time.
During WWII they had War Time, just as Britain had Double Summer Time, with Summer Time through the winters. $ for j in America/New_York EST5EDT Europe/London;\ > do TZ="$j" date -d @$(TZ=UT date +'%s' -d '1940-01-01'); done Sun Dec 31 19:00:00 EST 1939 Sun Dec 31 19:00:00 EST 1939 Mon Jan 1 00:00:00 GMT 1940 $ for j in America/New_York EST5EDT Europe/London;\ > do TZ="$j" date -d @$(TZ=UT date +'%s' -d '1943-01-01'); done Thu Dec 31 20:00:00 EWT 1942 Thu Dec 31 20:00:00 EWT 1942 Fri Jan 1 01:00:00 BST 1943 $ for j in America/New_York EST5EDT Europe/London;\ > do TZ="$j" date -d @$(TZ=UT date +'%s' -d '1943-06-01'); done Mon May 31 20:00:00 EWT 1943 Mon May 31 20:00:00 EWT 1943 Tue Jun 1 02:00:00 BDST 1943 $ But there are periods when the timezones America/New_York and EST5EDT diverge: $ for j in America/New_York EST5EDT;\ > do TZ="$j" date -d @$(TZ=UT date +'%s' -d '1966-06-24');done Thu Jun 23 20:00:00 EDT 1966 Thu Jun 23 19:00:00 EST 1966 $ > However since these rules are specific to US, I would prefer IANA > identifiers like America/New_York. I don't know who maintains the legacy EST5EDT zone, or for whom; the quotation below suggests that it may just follow New Jersey. For a long period after the war, it seems the timezones in the US were all over the place. > https://naggum.no/lugm-time.html > Erik Naggum. A Long, Painful History of Time. 1999 > > 8.2 Timezone Representation > > > > David Ols[o]n of Digital Equipment Corporation has laid down a tremendous > > amount of work in collecting the timezones of the world and their > > daylight saving time boundaries. Contrary to the Unix System V approach > > from New Jersey (insert appropriate booing for best effect), which > > codifies a daylight saving time regime only for the current year, and > > apply it to all years, David Ols[o]n's approach is to maintain tables of > > all the timezone changes. Cheers, David.
