While PiDay is said to have many originators, this is the PiDay website that I use. There are widgets here, along with suggested lessons, activities and pictures from teachers, parents and the general public. It is considered a valuable resource among teachers who have used it. Please add your links for Pi Day and widen the learning opportunities.

What makes this a widget and not a badge or button?

A badge (aka button) usually has ONLY a link.
A widget has a link AND some other program attached to it. In the case of the PiDay widget, it is a countdown calendar.

There are two sizes of Pi Day widgets currently available:

One is wide and can go on the side of a blog or in a website:

Pi Day Countdown

The other is a very small badge type widget, sometimes called a chiclet:

Pi Day Countdown