The purpose of this application is to help users to learn the history of the world from 1900 to present. Users will be able to select a particular year, and learn what happened in that year, and what events led to the year they chose.

There are two options: Which came first? and When did it happen?. Users can choose to learn the events of one subject area, such as warfare or politics, science or exploration, or arts and culture. The second option allows users to choose multiple subject areas, such as all the events of the period from 1900 to present. 

The application also allows users to learn the order of events, and the specific events of the chosen year. 

To learn the history of the world, users can select a year, and learn what happened in that year. 

This application allows users to get a sense of the order of historical events, and can be customized to a specific time period. 

This application is useful for learning the history of the world, from the year 1900 to present.