Abstract: Systems and methods are provided for determining the likelihood of a user's attendance at an event. For example, the systems and methods can be used to determine that a particular user is attending, is planning to attend, has already attended, or is about to attend a particular event, such as a movie, concert, tour, etc. Further, upon determining that a user is attending, has already attended, or is about to attend an event, systems and methods can be used to serve to a device, associated with the user, content that is related to the event. For example, the content may include invites that invite the user to provide a review of the event and to join a discussion about the event. Further, for example, the content may include links to websites that provide reviews and other information about the event, provide information about related events, or that offer related items for sale.