var now = moment(),
     second = now.seconds() * 6,
     minute = now.minutes() * 6 + second / 60,
     hour = ((now.hours() % 12) / 12) * 360 + 90 + minute / 12;


    $('#hour').css("transform", "rotate(" + hour + "deg)");
    $('#minute').css("transform", "rotate(" + minute + "deg)");
    $('#second').css("transform", "rotate(" + second + "deg)");

hour = ((now.hours() % 12) / 12) * 360 + 90 + minute / 12;

这个hour的角度，为什么要加上90度