Set up Locality, Date Format and Currency

If you are in U.S.A. or have installed another language pack the following changes might not be necessary.
Open the main language file
Tools => Define Languages => english.php
Phoenix is set for U.S.A. English with USD currency and m/d/y date format by default.

Set Up Locality

Find the following lines:

// 'en_US.UTF-8', 'en_US.UTF8', 'enu_usa'
// 'en_GB.UTF-8', 'en_GB.UTF8', 'eng_gb'
// 'en_AU.UTF-8', 'en_AU.UTF8', 'ena_au'
@setlocale(LC_ALL, array('en_US.UTF-8', 'en_US.UTF8', 'enu_usa'));

Change the code within the brackets in the last line to one of the options shown above it.

E.g. for Great Britain change to

@setlocale(LC_ALL, array('en_GB.UTF-8', 'en_GB.UTF8', 'eng_gb'));

Set the Date Format

Find the following lines:

define('DATE_FORMAT_SHORT', '%m/%d/%Y');  // this is used for strftime()
define('DATE_FORMAT', 'm/d/Y'); // this is used for date()
define('JQUERY_DATEPICKER_FORMAT', 'mm/dd/yy'); // see http://docs.jquery.com/UI/Datepicker/formatDate

Change them to:

define('DATE_FORMAT_SHORT', '%d/%m/%Y');  // this is used for strftime()
define('DATE_FORMAT', 'd/m/Y'); // this is used for date()
define('JQUERY_DATEPICKER_FORMAT', 'dd/mm/yy'); // see http://docs.jquery.com/UI/Datepicker/formatDate

Find the following lines:

return substr($date, 3, 2) . substr($date, 0, 2) . substr($date, 6, 4);
} else {
return substr($date, 6, 4) . substr($date, 0, 2) . substr($date, 3, 2);

Change them to:

return substr($date, 0, 2) . substr($date, 3, 2) . substr($date, 6, 4);
} else {
 return substr($date, 6, 4) . substr($date, 3, 2) . substr($date, 0, 2);

Set the Currency

Find the following line:

define('LANGUAGE_CURRENCY', 'USD');

E.g. for Great Britain change to:

define('LANGUAGE_CURRENCY', 'GBP');

To find your 3 letter currency code, internet search ISO 4217 Codes.

Repeat the changes above for the admin main language file, youradmin/includes/languages/english.php
You will need to access this language file using your FTP software e.g. Filezilla - it is not accessible from admin.