Participants wore a smartphone, which collected GPS, audio,accelerometry and image data, in a pouch around their necksfor a period of two weeks. After a retention interval of oneweek, they were asked to judge the specific day on whicheach of a selection of images was taken. To account forpeople’s judgements, we proposed a mixture model of fourprocesses - uniform guessing, a signal detection process basedon decaying memory strength, a week confusion process anda event confusion process in which the sensor streams wereused to calculate the similarity of events. A model selectionexercise testing all possible subsets of the processes favoureda model that included only the event confusion model. GPSsimilarities were found to be the most significant predictors,followed by audio and accelerometry similarities and thenimage similarities.