This is a Age icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,600 icons, all in the same style and quality.
The appears the be a calendar or notepad. It is a square with two triangles on it. One triangle points up and there is another triangle directly under it that points down. Both triangles are the same size as each other. There are two pegs on the top of the image.