Limited-Time Events are competitions with a variety of gameplay goals that must be accomplished in a certain time frame. The winners of Limited-Time Events will receive rewards of $ROC, $ROL, and rare Blockstars and Limited Edition Items.
There are many types of Limited-Time Events, each rewarding a different style of gameplay. For example, a particular Limited-Time Event might reward players who achieve the maximum number of #1 Singles in a given time period, while another Limited-Time Event might reward players who level up a Blockstar the most in a given time period.
There can be multiple Limited-Time Events running concurrently, and players are automatically eligible for each of them. Many Limited-Time Events simply reward regular gameplay, with no special exertions required by players. Other Limited-Time Events will require very specific actions by players to be successful.