<code>time_t</code> integer clock counts every <abbr>TAI</abbr> second,
as opposed to the default <code>"posix"</code> configuration
where the internal clock ignores leap seconds.
The two configurations agree for timestamps starting with 1972-01-01 00:00:00
<abbr>UTC</abbr> (<code>time_t</code> 63&thinsp;072&thinsp;000) and diverge for
timestamps starting with <code>time_t</code> 78&thinsp;796&thinsp;800,
which corresponds to the first leap second
1972-06-30 23:59:60 <abbr>UTC</abbr> in the <code>"right"</c