If you start to developing a language pack, you should make a copy of the en.utf8 language pack.

tar zcvf lang_XXXXX.tar.gz `find -type d -iname 'en.utf8' ->> creates a file with all folders and files to translate

create a new subfolder for your language pack and extraxt the tar file.

find -depth -type d -iname "en.utf8" -exec rename 's/en.utf8/xx.utf8/' {} \; ->> rename all en.utf8 folder to your xx shortcut

edit lang/xx.utf8/langconfig.php for your language:
$string['parentlanguage'] = '';
$string['strftimedate'] = '%%d %%B %%Y';
$string['strftimedateshort'] = '%%d %%B';
$string['strftimedatetime'] = '%%d %%B %%Y, %%I:%%M %%p';
$string['strftimedaydate'] = '%%A, %%d %%B %%Y';
$string['strftimedaydatetime'] = '%%A, %%d %%B %%Y, %%I:%%M %%p';
$string['strftimedayshort'] = '%%A, %%d %%B';
$string['strftimedaytime'] = '%%a, %%H:%%M';
$string['strftimemonthyear'] = '%%B %%Y';
$string['strftimerecent'] = '%%d %%b, %%H:%%M';
$string['strftimerecentfull'] = '%%a, %%d %%b %%Y, %%I:%%M %%p';
$string['strftimetime'] = '%%I:%%M %%p';
$string['strfdaymonthyearshort'] = '%%d/%%m/%%Y';
$string['thislanguage'] = 'English';

Modify $string['thislanguage'] = 'XXXXXXXX'; ->> entry in the dropdown-menu for your language

Adjust the other settings.

Additionally you need to translate the language strings for several xx_i18n() functions. I will ask Nigel to provide a file with all this array strings.

HTH

Heinz