* theory.html: Don’t imply that EST5EDT is an OK POSIX TZ string, as POSIX does not specify the DST transitions in this case. Use past tense to describe the typical pre-POSIX behavior. Minor copyediting. --- theory.html | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) diff --git a/theory.html b/theory.html index 53f7cee..298972e 100644 --- a/theory.html +++ b/theory.html @@ -874,15 +874,15 @@ an older <code>zic</code>. <pre><code>TZ='Pacific/Auckland'</code></pre> </li> <li> - POSIX does not define the exact meaning of <code>TZ</code> values like + POSIX does not define the <abbr>DST</abbr> transitions + for <code>TZ</code> values like "<code>EST5EDT</code>". - Typically the current <abbr>US</abbr> <abbr>DST</abbr> rules - are used to interpret such values, but this means that the - <abbr>US</abbr> <abbr>DST</abbr> rules are compiled into each - program that does time conversion. - This means that when - <abbr>US</abbr> time conversion rules change (as in the United - States in 1987), all programs that do time conversion must be + Traditionally the current <abbr>US</abbr> <abbr>DST</abbr> rules + were used to interpret such values, but this meant that the + <abbr>US</abbr> <abbr>DST</abbr> rules were compiled into each + program that did time conversion. This meant that when + <abbr>US</abbr> time conversion rules changed (as in the United + States in 1987), all programs that did time conversion had to be recompiled to ensure proper results. </li> <li> @@ -893,14 +893,14 @@ an older <code>zic</code>. <li> In POSIX, there is no tamper-proof way for a process to learn the system's best idea of local wall clock. - (This is important for applications that an administrator wants + This is important for applications that an administrator wants used only at certain times – without regard to whether the user has fiddled the <code>TZ</code> environment variable. While an administrator can "do everything in <abbr>UT</abbr>" to get around the problem, doing so is inconvenient and precludes - handling daylight saving time shifts - as might be required to - limit phone calls to off-peak hours.) + handling daylight saving time shifts – as might be required to + limit phone calls to off-peak hours. </li> <li> POSIX provides no convenient and efficient way to determine @@ -923,7 +923,7 @@ an older <code>zic</code>. Unsigned 32-bit integers are used on one or two platforms, and 36-bit and 40-bit integers are also used occasionally. Although earlier POSIX versions allowed <code>time_t</code> to be a - floating-point type, this was not supported by any practical systems, + floating-point type, this was not supported by any practical system, and POSIX.1-2013 and the <code><abbr>tz</abbr></code> code both require <code>time_t</code> to be an integer type. </li> @@ -960,9 +960,9 @@ an older <code>zic</code>. separately maintaining both <code>TZ</code> and <code>TIMEZONE</code> seemed a nuisance; and systems where "new" forms of <code>TZ</code> might cause problems can simply - use <code>TZ</code> values such as "<code>EST5EDT</code>" which - can be used both by "new" programs (à la POSIX) and "old" - programs (as zone names and offsets). + use legacy <code>TZ</code> values such as "<code>EST5EDT</code>" which + can be used by "new" programs as well as by "old" programs that + assume pre-POSIX <code>TZ</code> values. </p> </li> <li> -- 2.17.0