This Monday 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 4,400 icons, all in the same style and quality.
A square with the Capital letter M lower case O inside of it. On top of the square is a smashed rectangle that has 2 vertical tiny rectangle coming out of the top. Similar to what a desk flip calendar would be