A nice and useful collection for calendar icon making.
To design something unique you might find useful some related tutorials.
Calendar icons not only for your blog
Wit CSS-code and a source image for GIMP.
Web 2.0 Date Icons For Your Blog
png-format with a .psd-source.
Calendar Icon Tutorial
Calendar Icon
Calendar icon – Photoshop tutorial
Creating a Blog Entry Date Calendar Icon Look with CSS, Mostly
Pingback: Gallery Of Date Stamps And Calendars | Greep It