Style date in Genesis post info. This fixes a problem with post dates showing up as Jan 1st on all new posts from code previously found. CSS styles will need to be adjusted.

functions.php

<?php

add_filter( 'genesis_post_date_shortcode', 'child_post_date_shortcode', 10, 2 );
/**
 * Customize Post Date format and add extra markup for CSS targeting.
 */
function child_post_date_shortcode( $output, $atts ) {

    return sprintf(
        '<span class="date time published" title="%4$s">%1$s<span class="day">%2$s</span> <span class="date">%3$s</span> <span class="month">%4$s</span></span>',
        $atts['label'],
        get_the_time( 'D' ),
        get_the_time( 'd' ),
        get_the_time( 'M' ),
        get_the_time( 'D-d-M\TH:i:sO' )
    );

}

style.css

/*
Post Time and Date Display
---------------------------------------------------------------------------------------------------- */

.post-info {
    margin: 0 0 5px;
    padding: 5px 0 15px 0;
}

.post-info .time,
.post-info .time span {
    color: #FFF;
    font-family: sans-serif;
    font-size: 16px;
    font-size: 1.6rem;
    font-weight: normal;
    display: block;
    text-align: center;
    text-transform: uppercase;
    width: 78px;
}
.post-info .time {
    background: url(images/date-bg.jpg) no-repeat;
    clear: both;
    float: left;
    width: 99px;
    height: 81px;
    position: relative;
    top: -40px;
}

.post-info .date {
    font-size: 35px !important;
    font-size: 3.5rem !important;
    font-weight: bold !important;
    line-height: 1.0;
 }

.post-info .day {
    line-height: 1em;
    margin-top: 8px;
}
.post-info .month {
    margin-top: -3px;
    text-transform: uppercase;
}