The calendar is an image, which you'll have to right click on the image and select 'Save us Picture' chose your file format (.jpg or png are best) and upload it to your post/page, dragging it directly to your post will not help you, this is the safest and possible least painful way of doing it and avoiding code appearing in your content. Else you can create a form in wordpress and populate it with content within wordpress, easiest solution, if your theme provides you will styles for tables then your set, if not you'll need to implement that.