apply daylight saving only when date is on daylight saving time

[runico]

When daylight saving is activated one hour is added to all dates, but only should be added when the date is on daylight saving time. Now I must disable daylight saving and I will have to enable it in april.

[runico]

Patch for fix it

[tcat]

Here is an other way to calculate daylight saving time (doesn\'t depends on locale settings):

  //adjust daylight saving
  if ($CONFIG['dst_active']) {
    $year = date("Y", $timestamp);
    $tmp = strtotime("last Sunday", mktime(0, 0, 0, 4, 1, $year));
    $last_sunday_march = mktime(2, 0, 0, date("m", $tmp), date("d", $tmp), date("Y", $tmp));
    $tmp = strtotime("last Sunday", mktime(0, 0, 0, 11, 1, $year));
    $last_sunday_october = mktime(3, 0, 0, date("m", $tmp), date("d", $tmp), date("Y", $tmp));
    if (($timestamp >= $last_sunday_march) && ($timestamp + 3600 < $last_sunday_october)) $timestamp += 3600; //summertime
  }

[jpingle]

DST is changing this year in the US, and changes in other locations from time to time. Hardcoding dates is probably not a good idea.

Part of the issue with this ticket is whether a system's clock is set to UTC, in which case the system doesn't know or care about DST, of if the system clock is set to Local Time in which case no changes to the clock need to be made.

If you hardcode DST, instead of relying on the system's time zone definitions, it may fix it for some people and break it for others. You could end up an hour or two off in any direction, if people on the same system were in wildly different places.

[seansan]

Review in 1.1

[till]

I see what you mean. I'll look into this.

[till]

This is extremely hard to guess.

date('I', $foo)

Should return 1 or 0, if a date is in DST, or not. A TZ has to be set for this.

[alec]

I think it should be hardcoded.

[ulysses.almeida]

I think we better use timezone support from PHP 5.1.0 and above. Users could choose a timezone from timezone_identifiers_list(); Than roundcube can calculate better when some date is or not in DST considering users timezone. The only tradeoff is, RC admins will need to keep their timezonedb updated, because, as already mentioned, some countries change their DST yearly. But probably he already need to keep his server tzdb updated.