From this article, you will get know how to configure a module so that when you translate a site to other languages plural forms work correctly.

Solution:

You need to specify the following in the code:

format_plural($day_count, ‘1 day’, ‘@count days’);

Format of format_plural() function:

D6: format_plural($count, $singular, $plural, $args = array(), $langcode = NULL)
D5: format_plural($count, $singular, $plural)

Parameters

• $count – a number to show
• $singular – line for singular. Don’t use @count there.
• $plural – line for plural. Use @count instead of a number. E.g. , “@count new comments”.
• $args – associative array of replacements which are made after translation (there is no such parameter in Drupal 5 or less). Incidences of any key in this array are replaced with the corresponding value. Based on the first character of the key, the value is escaped and/or themed:
  • !variable: inserted as is
  • @variable: escape plain text to HTML (check_plain)
  • %variable: escape text and theme as a placeholder for user-submitted content (check_plain + theme_placeholder)

  Note: you don’t need to include @count to this array. This is an automatic replacement for plural forms.

• $langcode – un-compulsory language code for translating to a language which is not used to show a page (there is no such parameter in Drupal 5 or less).

Example:

$output = format_plural($update_count,
‘Changed the content type of 1 post from %old-type to %new-type.’,
‘Changed the content type of @count posts from %old-type to %new-type.’,
array(‘%old-type’ => $info->old_type, ‘%new-type’ => $info->new_type)));

po-file will contain the following code then:

msgid “1 day”
msgid_plural “@count days”
msgstr[0] “@count day”
msgstr[1] “@count days”
msgstr[2] “@count days”

Good luck!