An activity tracking system includes a sensor device and a display device. The sensor device is configured to be carried by the user and includes at least one sensor configured to obtain the activity data for the user. The display device includes a display screen. The display device is configured to receive the activity data obtained by the sensor device and display the activity data about a circular axis on the display screen. The activity data includes sleep data on one side of the circular axis and awake data on an opposite side of the circular axis. The sleep data includes a start time and an end time for a daily retired sleep period, the end time occurring in a selected day and the start time occurring in a previous day.