Re: displaying Date using local timezone

[Ralph Corderoy]

Hi,

Bob wrote:
> I found that (zone) provides you your "standard time" UTC offset (in
> minutes), regardless of (dst)'s result.

nmh's code seems to assume DST means clocks wind forward sixty minutes,
which isn't always true, e.g.

    $ TZ=Australia/Lord_Howe date -d '01 Aug'
    2021-08-01 00:00:00 +1030 Sun
    $ TZ=Australia/Lord_Howe date -d '01 Feb'
    2021-02-01 00:00:00 +1100 Mon

One example is dlocaltime():

    #ifdef HAVE_STRUCT_TM_TM_GMTOFF
        tw.tw_zone = tm->tm_gmtoff / 60;
        if (tm->tm_isdst)                   /* if DST is in effect */
            tw.tw_zone -= 60;               /* reset to normal offset */
    #else
        {
            static bool deja_vu;

            if (!deja_vu) {
                deja_vu = true;
                tzset();
            }
        }
        tw.tw_zone = -(timezone / 60);
    #endif

Of ‘timezone’ in the #else branch, tzset(3p) says

   ‘The external variable timezone shall be set to the difference, in
    seconds, between Coordinated Universal Time (UTC) and local standard
    time.’

-- 
Cheers, Ralph.