A mobile device enables its user to retroactively “check in,” on social media, to locations to which the device has previously been. The mobile device automatically tracks the locations to which it goes during some time interval. As the mobile device goes to each location, the mobile device stores data that specifies that location. Following the time interval, and potentially in response to a request by the device's user to view the locations previously visited, the mobile device presents a list of at least some of the locations on its display. The device's user can select one or more of the presented locations. The selection of a location causes the mobile device to post, to an Internet-based social media service, information pertaining to the selected location. For example, such information can indicate that the device's user had been at the selected location.