This is the Minus 1 Dzień 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 what looks like a small, desktop calendar, with two rings on the top to change the date. It has "- 1d" meaning to subtract one day, written on the front of the calendar, to be an icon representing the subtraction of a day for other calendar purposes.