I have a couple functions that I use to make human friendly time formats with PHP. The first one is fairly straight forward:

function human_time_format($datetime)
{
    return date('F j, Y @ g:i a', strtotime($datetime));
}

Example result:

March 6, 2012 @ 1:50 am

The next function is a bit more complex, and generates a relative time format:

function relative_time_format($datetime)
{
    $difference = time() - strtotime($datetime);
    $periods = array('second', 'minute', 'hour', 'day', 'week', 'month', 'year', 'decade');
    $lengths = array(60, 60, 24, 7, 4.35, 12, 10);

    // This was in the past.
    if ($difference > 0)
    {
        $ending = 'ago';
    }
    // This is in the future.
    else
    {
        $difference = -$difference;
        $ending = 'from now';
    }

    for ($j = 0; $difference >= $lengths[$j]; $j++)
        $difference /= $lengths[$j];

    $difference = round($difference);

    if ($difference != 1)
        $periods[$j] .= 's';

    return $difference . ' ' . $periods[$j] . ' ' . $ending;
}

Example result:

1 minute ago