var tNow = '2012.7.13 16:16';
var tSpare = '3天4时22分';
alert(getStartTime(tNow, tSpare)); //2012年7月9日20时38分上架

function getStartTime(tNow, tSpare) {
    var dNow = new Date(tNow.replace(/\./g, "/"));
    var ar = tSpare.match(/[0-9]+/g);
    var d = new Date();
    d.setTime(dNow.getTime() - ((7 - ar[0]) * 86400 - ar[1] * 3600 - ar[2] * 60) * 1000);
    return d.getFullYear() + '年' + (d.getMonth() + 1) + '月' + d.getDate() + '日' + d.getHours() + '时' + d.getMinutes() + '分上架';
}