WordPress/wp-includes/locale.php

<?php
// Date and Time

// The Weekdays
$weekday[0] = __('Sunday');
$weekday[1] = __('Monday');
$weekday[2] = __('Tuesday');
$weekday[3] = __('Wednesday');
$weekday[4] = __('Thursday');
$weekday[5] = __('Friday');
$weekday[6] = __('Saturday');

// The first letter of each day.  Note that marking single characters for
// translation is useless, but here it is.
$weekday_initial['Sunday']    = __('S');
$weekday_initial['Monday']    = __('M');
$weekday_initial['Tuesday']   = __('T');
$weekday_initial['Wednesday'] = __('W');
$weekday_initial['Thursday']  = __('T');
$weekday_initial['Friday']    = __('F');
$weekday_initial['Saturday']  = __('S');

// Abbreviations for each day.
$weekday_abbrev['Sunday']    = __('Sun');
$weekday_abbrev['Monday']    = __('Mon');
$weekday_abbrev['Tuesday']   = __('Tue');
$weekday_abbrev['Wednesday'] = __('Wed');
$weekday_abbrev['Thursday']  = __('Thu');
$weekday_abbrev['Friday']    = __('Fri');
$weekday_abbrev['Saturday']  = __('Sat');

// The Months
$month['01'] = __('January');
$month['02'] = __('February');
$month['03'] = __('March');
$month['04'] = __('April');
$month['05'] = __('May');
$month['06'] = __('June');
$month['07'] = __('July');
$month['08'] = __('August');
$month['09'] = __('September');
$month['10'] = __('October');
$month['11'] = __('November');
$month['12'] = __('December');

// Abbreviations for each month.
$month_abbrev['January'] = __('Jan');
$month_abbrev['February'] = __('Feb');
$month_abbrev['March'] = __('Mar');
$month_abbrev['April'] = __('Apr');
$month_abbrev['May'] = __('May');
$month_abbrev['June'] = __('Jun');
$month_abbrev['July'] = __('Jul');
$month_abbrev['August'] = __('Aug');
$month_abbrev['September'] = __('Sep');
$month_abbrev['October'] = __('Oct');
$month_abbrev['November'] = __('Nov');
$month_abbrev['December'] = __('Dec');
?>