Random "month & day" with JS
function randNum(limit){var r=Math.floor(Math.random()*limit)+1;return r;}


Can be shortened to:

function randNum(limit){return Math.floor(Math.random()*limit)+1;}


You should also declare your variables outside of the setInterval and then set them inside only if you need to (for example, the days_array never changes so only needs to be decalared once and not every second.