format_date() doesn't return localized year correctly

No, it returns "2007". For "%EY" and "%Ey", I found in POSIX strftime() and it works well in Thailand. Most of us use %EY but some people solve this problem by hardcode adding 543 to 2007 to obtain 2550.

@Pasqualle

Sure! My patch above relies on system locale which may be set by setlocale(LC_CTIME, 'th_TH.UTF8') in settings.php. That means for India, you just need to call setlocale(LC_CTIME, 'ar_IN.UTF8') instead.

Anyway, I found another effect right now. format_date() is also called to format the date in input field. Passing 2550 to strtotime() will result in invalid date because strtotime() doesn't recognize locale year. So handling Y and y for locale year might be not a good idea.

What if we use another character for locale year, e.g., "X" or "c"? And then let users define custom date/time format to replace "Y" by the new one?

Another option is to write drupal_strtotime() which replace %EY by %Y before calling strtotime() as usual.

Any comment?

I found better solution by adding 'X' and 'x' for locale year and let users specify custom date format in settings.php. As a result, date in most pages displays correctly. I applied this new patch to http://drupal.in.th/ and it works without annoying issue.

setlocale(LC_TIME, 'th_TH.UTF8');
$conf = array(
  'date_format_short' => 'm/d/X - H:i',
  'date_format_large' => 'l, F j, X - H:i',
  'date_format_medium' => 'D, m/d/X - H:i',
);

There are still issue regarding date input format but replacing strtotime() seems like a big effort.

It would be nice to have this patch in Drupal 6 timeframe. Is it possible?

@Gábor

Good point. If PHP introduces X, they just conflict. date() itself does not support locale date format so there is no systematic approach to extend format chars like %EY in strftime(). So I need to find better approach.

1. Adding a special prefix % to interpret %Y and %y using strftime() to obtain localized year.
2. Changing format chars based on date() to strftime() instead.