This is the Kalendarz 29 icon for Windows 10. Here we go. Optimized for 32x32 px, these are the simplest icons in the line style. Downloadable formats are PNG and SVG, among others. Icons8 icon pack is unique in providing a huge number of icons designed by the same team of four designers who create the new icons every working day in the same style and with the same quality. Same cool as the Bat Face, huh.
It's a square with 2 ring-like objects at the top, to indicate that it's a calendar that you would flip to change the date each day. There is the number 29 inside the square, to signify that it is the 29th day of the month.