This page shows the different variations of the Kalendarz 13 from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free. Icons are available in PNG and vector.
The image is of a notepad or calendar with the number thirteen. There are two little tabs at the top of a square which would be the binds for the notepad or calendar. The number 13 is just centered in the bigger part of the square sheet.