This Notification 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 5,100 icons, all in the same style and quality.
We've received the idea on November 26, 2012 and created the icons on February 24, 2013
A set of icons for viewing a calendar/schedule, appointment reminders, recurring appointment icon, "show as" icon, categorize icon, along with priority icons (high, low and private). See this screenshot for concepts: