This Calendar 26 icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 4,600 icons, all in the same style and quality.
It's an icon of a calendar, set on the 26th day of the month. It's displayed as a square with two ring-like objects at the top, to indicate that the pages flip over. There is the number 26 in the center of the square.