1. A method comprising: determining, by a computing device, a previously outputted content item that has been previously output at a first time; determining, by the computing device, a content item to be considered for recommendation; determining, by the computing device, a value indicating a time difference between a reference time associated with the content item and the first time associated with the previously outputted content item; determining, by the computing device, a contribution factor for the previously outputted content item based on proximity of the value indicating the time difference to each of a first multiple of a first time period and a second multiple of a second time period; determining, by the computing device, a recommendation score for the content item based, at least in part, on the contribution factor; and outputting a signal comprising a recommendation based on the determined recommendation score for the content item.