It's a logo of a calendar page with two rings on top and then the page hanging down from them. There is a line across the top of the page and in the lower bigger section is the number "23".
This Calendar 23 icon is made in flat color style
. This format was developed by Icons8 designer team and became immensely popular for use in web and mobile applications. Feel free to download this icon in PNG format for free, or unlock other formats for $5. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 6,000 icons, all in the same style and quality.