Change the dates returned by Tumblr's tweet.js callback to something like 12:00 PM Oct. 27th

prettyTweetDateForTumblr.js

var prettyTweetDate = function(tweetDateFromJSON) {
    var tweetDate = new Date(Date.parse(tweetDateFromJSON)),
        tweetHours = tweetDate.getHours();

    tweetHours = (tweetHours < 13) ? tweetHours : tweetHours - 12;

    var tweetDateSuffix = function(day) {
      switch (day) {
        case 1: case 21: case 31:
          return "st"; break;
        case 2: case 22:
          return "nd"; break;
        case 3: case 23:
          return "rd"; break;
        default:
          return "th";
      }
    };
    
    return  tweetHours + ":" + 
            tweetDate.getMinutes() + " " + 
            ((tweetHours < 12) ? "AM" : "PM") + " " + 
            ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"][tweetDate.getMonth()] + " " + 
            tweetDate.getDate() + 
            tweetDateSuffix(tweetDate.getDate());
};

// For testing...
console.log(prettyTweetDate("Jan 3, 1975 2:14 AM"));
console.log(prettyTweetDate("Feb 4, 1975 2:14 AM"));
console.log(prettyTweetDate("March 22, 1975 2:14 PM"));
console.log(prettyTweetDate("April 19, 1975 2:14 AM"));

Refactoring, for fun... :P